Medical protective clothing materials

ABSTRACT

Protective clothing materials and related methods and garments are provided. In some embodiments, a protective clothing material may comprise a fibrous layer that serves as a barrier to certain fluids (e.g., bodily fluids, water) and microbes. The impermeability of the fibrous layer may be due, at least in part, to the structural uniformity and/or relatively small pore size of the fibrous layer. In some embodiments, the fibrous layer may have a relatively high air permeability that imparts beneficial properties (e.g., relatively high air flow, breathability) to the protective clothing material without adversely affecting its protection rating. In certain embodiments, the protective clothing material may also comprise one or more coarse nonwoven webs that impart beneficial properties (e.g., splash resistance) to the protective clothing material. The protective clothing materials, described herein, may be particularly useful for a wide variety of applications, including the formation of AAMI level 4 protective garments.

FIELD OF INVENTION

The present embodiments relate generally to protective clothingmaterials, and specifically, to protective clothing materials thatprevent and/or are impermeable to penetration by certain fluids andmicrobes.

BACKGROUND

Healthcare workers are at risk of exposure to pathogenic microbes viacontact with bodily fluids (e.g., blood, urine, saliva, sweat, feces,vomit, breast milk, semen) or other carriers (e.g., lint, sloughedskin). The use of protective clothing (e.g., surgical gowns, surgicalhoods, isolation gowns, and coveralls) that act as a barrier to bodilyfluids and other carriers eliminate or reduce exposure, and thereforeprevent the transfer of pathogenic microbes between, e.g., patients andhealthcare workers. However, the use of defective or inappropriateprotective clothing may result in the unintended penetration of acarrier through the clothing (e.g., strikethrough) and the subsequentability for microbes present in the carrier to directly contact thewearer. Depending on the application, protective clothing may bedesigned to offer different levels of protection from carriers andmicrobes.

SUMMARY OF INVENTION

Protective clothing materials that prevent and/or are impermeable topenetration by certain fluids and microbes, and related components,systems, and methods associated therewith are provided. The subjectmatter of this application involves, in some cases, interrelatedproducts, alternative solutions to a particular problem, and/or aplurality of different uses of structures and compositions.

In some aspects, a protective clothing material is provided. Thematerial comprises a fibrous layer comprising synthetic fibers. A meanflow pore size of the fibrous layer is greater than or equal to about 1micron and less than or equal to about 6 microns. A maximum pore size ofthe fibrous layer is greater than or equal to about 4 micron and lessthan or equal to about 12 microns. A difference between the maximum poresize and the mean pore size is less than or equal to about 6 microns. Anair permeability of the fibrous layer is greater than or equal to about4 CFM and less than or equal to about 10 CFM.

In some aspects, a protective clothing material is provided. Thematerial comprises a fibrous layer comprising synthetic fiber. A meanflow pore size of the fibrous layer is greater than or equal to about 1micron and less than or equal to about 6 microns. A standard deviationof the mean flow pore size of the fibrous layer is greater than or equalto about 0 microns and less than or equal to about 1 micron. A standarddeviation of an air permeability of the fibrous layer is greater than orequal to about 0 CFM and less than or equal to about 1 CFM.

In some aspects, a protective clothing material is provided. Thematerial comprises a first coarse fiber layer and a second coarse fiberlayer. The material further comprises a fibrous layer positioned betweenthe first and the second coarse fiber layers.

The fibrous layer comprises a meltblown fiber web, has a mean flow poresize of greater than or equal to about 1 micron and less than or equalto about 6 microns, has an air permeability of greater than or equal toabout 1 CFM and less than or equal to about 10 CFM, and has a basisweight of greater than or equal to about 10 g/m² and less than or equalto about 50 g/m².

In some aspects, a method of forming a protective clothing material isprovided. The method comprises providing a plurality of nonwoven websand calendering the plurality of nonwoven webs to form a fibrous layer.The fibrous layer has an air permeability of greater than or equal toabout 4 CFM and less than or equal to about 10 CFM, an air permeabilityuniformity of the layer is greater than or equal to about 0 and lessthan or equal to about 1, and a mean flow pore size of greater than orequal to about 1 micron and less than or equal to about 6 microns. Themethod further comprises adhering a coarse fiber layer to at least onesurface of the fibrous layer using an adhesive.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 is a schematic of a protective clothing material according tocertain embodiments;

FIG. 2 is a schematic of a protective clothing material according tocertain embodiments;

FIG. 3 is a schematic of a protective clothing material according tocertain embodiments;

FIG. 4 is a schematic of a protective clothing material according tocertain embodiments;

FIG. 5A is a schematic of a modified nonwoven web, according to one setof embodiments;

FIG. 5B is a schematic of a modified layer, according to certainembodiments;

FIG. 6A is scanning electron microscope images of a fibrous layer beforecalendering (top) and after calendering (bottom) according to one set ofembodiments;

FIG. 6B is scanning electron microscope images of a fibrous layer beforecalendering (top) and after calendering (bottom) according to one set ofembodiments;

DETAILED DESCRIPTION

Protective clothing materials and related methods and garments areprovided. In some embodiments, a protective clothing material maycomprise a fibrous layer that serves as a barrier (e.g., impermeablebarrier) to certain fluids (e.g., bodily fluids, water) and microbes(e.g., bacteria, fungi, viruses). The barrier properties of the fibrouslayer may be due, at least in part, to the structural uniformity (e.g.,pore size uniformity, air permeability uniformity), suitable basisweight, and/or relatively small pore size (e.g., mean flow pore size,maximum pore size) of the fibrous layer. In some embodiments, thefibrous layer may have a relatively high air permeability that impartsbeneficial properties (e.g., relatively high air flow, breathability) tothe protective clothing material without adversely affecting itsprotection rating (e.g., ANSI/AAMI level 4). In certain embodiments, theprotective clothing material may also comprise one or more coarse fiberlayers (e.g., spunbond web) that imparts beneficial properties (e.g.,splash resistance) to the protective clothing material. The protectiveclothing materials, described herein, may be particularly useful for awide variety of applications, including the formation of ANSI/AAMI level4 protective garments (e.g., surgical apparel, surgical drapes, surgicalgowns, surgical hoods).

Many clinical environments require healthcare workers to wear protectiveclothing that meet certain protection level standards. For example,during surgical operations, healthcare workers need to wear the AmericanNational Standards Institute (i.e., ANSI)/Association for theAdvancement of Medical Instrumentation (i.e., AAMI) level 4 (i.e.,highest protection level) protective clothing. In some existingprotective clothing, a tradeoff exists between protection rating (e.g.,level 4) and features important to wearability (e.g., comfort), such aslight weight, breathability, and good air permeability. For instance,some existing protective clothing utilizes a thin polymer film to formlightweight level 4 protective clothing. However, the thin polymer filmcan significantly reduce air permeability and/or breathability (e.g.,moisture vapor transmission rate). During long surgical operations(e.g., 2-12 hours), the low exchange of heat and/or sweat as a result oflow air permeability and/or breathability can adversely affect asurgeon's performance. Accordingly, there is a need for protectiveclothing that can achieve the requisite protection rating for a givenapplication without sacrificing wearablity.

In some embodiments, a fibrous layer having a relatively low pore size(e.g., mean flow pore size, maximum pore size), suitable basis weight,and/or high structural uniformity can be used to produce protectiveclothing material having the requisite protection rating and goodwearability (e.g., comfort). Protective clothing comprising such afibrous layer as described herein, does not suffer from one or morelimitations of existing protective clothing. Without being bound bytheory, it is believed that the relatively small pore size serves toreduce or eliminate the transmission of fluids (e.g., bodily fluids) andmicrobes. A fibrous layer having a relatively large pore size may allowfor the penetration of bodily fluids and microbes (e.g., strikethrough).It is also believed that the structural uniformity (e.g., in pore size,in air permeability) allows the fibrous layer to have relatively uniformresistance to transmission throughout the layer, and accordingly theprotective clothing material. Structural non-uniformity, such as arelatively large variance in pore size or air permeability, may resultin non-uniformity in the resistance to transmission throughout the layerand ultimately allow bodily fluids and/or microbes to penetrate at areasof low resistance. It is also believed that the suitable basis weights,described herein, allow the fibrous layer to have a sufficient fiberdensity to form a tortuous path that traps fluids and/or microbes whilemaintaining features important to wearability (e.g., light weight,breathability).

In some embodiments, a protective clothing material may comprise afibrous layer having a relatively small pore size (e.g., mean flow poresize, maximum pore size), a suitable basis weight, and/or highstructural uniformity. The fibrous layer may include one or morenonwoven webs (e.g., meltblown fiber webs). In some embodiments, two ormore nonwoven webs (e.g., two fiber webs, three fiber webs, four or morefiber webs) may form a fibrous layer. For instance, as illustrated inFIG. 1, a protective clothing material 5 may include a fibrous layer 10comprising two nonwoven webs. Fibrous layer 10 may include a firstnonwoven web 15 (e.g., meltblown fiber web) and a second nonwoven web 20(e.g., meltblown fiber web). In some embodiments, the first and/orsecond nonwoven webs may comprise synthetic fibers. For instance thefirst and/or second nonwoven webs comprise continuous synthetic fibersformed, e.g., by a meltblowing process. In certain embodiments, firstnonwoven web 15 may be directly adjacent to second nonwoven web 20 asshown in FIG. 1. As used herein, when a layer or fiber web is referredto as being “directly adjacent” to another layer or fiber web, it meansthat no intervening layer is present.

In some embodiments, first nonwoven web and second nonwoven web 20 maybe joined (e.g., via a calendering process) to form a fibrous layerhaving beneficial properties. For instance, in some embodiments, fibrouslayer 10 may have a relatively small mean flow pore size (e.g., greaterthan or equal to about 2 microns and less than or equal to about 5microns) and/or maximum pore size (e.g., greater than or equal to about6 microns and less than or equal to about 9 microns). The fibrous layermay also have a suitable basis weight (e.g., greater than or equal toabout 20 g/m² and less than or equal to about 40 g/m²). In someembodiments, fibrous layer 10 may be relatively lightweight, breathable,and/or permeable to air. For instance, fibrous layer 10 may have arelatively high air permeability (e.g., greater than or equal to about 4CFM and less than or equal to about 10 CFM), and/or a relatively highmoisture vapor transmission rate (e.g., greater than or equal to about1,000 g/m²day). In certain embodiments, the fibrous layer may berelatively thin (e.g., greater than or equal to about 1 mil and lessthan or equal to about 6 mils).

In some embodiments, fibrous layer 10 may be relatively structurallyuniform, such that the variance in or range of one or more structuralproperties when measured across the fibrous layer is relatively small.For instance, in some embodiments, the standard deviation in mean flowpore size when measured across the fibrous layer may be less than 1micron. The difference between the maximum pore size and the mean flowpore size may be relatively small (e.g., greater than or equal to about0 microns and less than or equal to about 10 microns). In some suchembodiments, the ratio of mean flow pore size to maximum pore size maybe greater than or equal to about 0.35 and less than or equal to about0.55. In certain embodiments, the standard deviation in air permeabilitywhen measured across the fibrous layer may be less than 1 CFM.

In some embodiments, three or more fiber webs may form a fibrous layer.For instance, as illustrated in FIG. 2, a protective clothing material25 may comprise a fibrous layer 30 including a first nonwoven web 35, asecond nonwoven web 40, and a third nonwoven web 45. The three nonwovenwebs may be joined (e.g., via a calendering process) to form a fibrouslayer having beneficial properties. In some embodiments, first nonwovenweb 35, second nonwoven web 40, and/or third nonwoven web 45 maycomprise synthetic fibers. In some such embodiments, the first nonwovenweb, the second nonwoven web, and/or the third nonwoven web comprisecontinuous synthetic fibers formed, e.g., by a meltblowing orelectrospinning process. For instance, first nonwoven web 35 and secondnonwoven web 40 may be formed by a meltblowing process. In some suchcases, third nonwoven web 45 may be formed by an electrospinningprocess. In other instances, third nonwoven web 45 may be formed by ameltblowing process. In certain embodiments, third nonwoven web 45 maybe positioned between first nonwoven web 35 and second nonwoven web 40.In some such embodiments, third nonwoven web 45 may be directly adjacentto first nonwoven web 35 and/or second nonwoven web 40 as shown in FIG.2. In other such embodiments, one or more intervening nonwoven webs maybe positioned between third nonwoven web 45 and first nonwoven web 35and/or second nonwoven web 40. Non-limiting examples of interveningnonwoven webs include meltspun webs (e.g., spunbond), centrifugal spunwebs, solvent spun webs, electroblown webs, gel spun webs, and nonwovenwebs comprising staple fibers.

In other embodiments, the fibrous layer may include a single fiber web.For instance, as shown in FIG. 3, a protective clothing material 50 mayinclude a fibrous layer 55 comprising a single nonwoven web (e.g.,meltblown fiber web).

In general, the fibrous layer may comprise any suitable number ofnonwoven webs (e.g., one nonwoven web, two nonwoven webs, three nonwovenwebs, four nonwoven webs, five nonwoven webs, six or more nonwovenwebs). Regardless of the number of nonwoven webs in the fibrous layer,the fibrous layer may have the properties described herein. Forinstance, in embodiments in which the fibrous layer comprises two ormore nonwoven webs, the nonwoven webs may be joined (e.g., via acalendering process) to produce a fibrous layer having the propertiesdescribed herein.

Regardless of the number of fiber webs in the fibrous layer, theprotective clothing material may optionally comprise one or more coarsefiber layers. For instance, as described further below, the fibrouslayer (e.g., a calendared fibrous layer) and one or more coarse fiberlayers may be joined (e.g., via non-calendering process, via anadhesive) to impart beneficial properties to the protective clothingmaterial. In some embodiments, the coarse fiber layers may include oneor more nonwoven webs. In some embodiments, a coarse fiber layer maycomprise a single nonwoven web (e.g., spunbond nonwoven web, cardednonwoven web, drylaid nonwoven web, wetlaid nonwoven web, spunlacenonwoven web). In other embodiments, the coarse fiber layer may comprisetwo or more nonwoven webs (e.g., two nonwoven webs, three nonwovenwebs). In some embodiments, the coarse fiber layer may comprise fibershaving a relatively large average diameter (e.g., greater than or equalto about 10 microns and less than or equal to about 50 microns). Incertain embodiments, the coarse fiber layer may comprise syntheticfibers and/or natural fibers. For instance, a coarse fiber layer maycomprise synthetic staple fibers.

In some embodiments, as illustrated in FIG. 4, a protective clothingmaterial 60 may include a first coarse fiber layer 65, a second coarsefiber layer 70, and a fibrous layer 75 comprising one or more nonwovenwebs (e.g., 80, 85, and/or 90). The fibrous layer 75 may be positionedbetween first coarse fiber layer 65 and second coarse fiber layer 70. Insome such embodiments, fibrous layer 75 may be directly adjacent to thefirst and/or second coarse fiber layer. In other such embodiments, oneor more intervening nonwoven webs or layers, as described above, may bepositioned between fibrous layer 75 and first coarse fiber layer 65and/or second coarse fiber layer 70. Non-limiting examples ofintervening nonwoven webs include meltspun webs (e.g., spunbond),centrifugal spun webs, solvent spun webs, electroblown webs, gel spunwebs, and nonwoven webs comprising staple fibers. In certainembodiments, fibrous layer 75 may include a first nonwoven web (e.g.,80) and a second nonwoven web (e.g., 85). In some embodiments, fibrouslayer 75 may include a third nonwoven web (e.g., 90) positioned betweena first nonwoven web (e.g., 80) and a second nonwoven web (e.g., 85). Inother embodiments, fibrous layer 75 may include a single fiber web(e.g., 80).

In some embodiments, first coarse fiber layer 65 and/or second coarsefiber layer 70 may be joined to fibrous layer 75, directly orindirectly. For example, first coarse fiber layer 65 and/or secondcoarse fiber layer 70 may be joined to fibrous layer 75 via an adhesive.For example, suitable adhesives include ethyl vinyl acetate (EVA),copolyesters, polyolefins, polyamides, polyurethanes, styrene blockcopolymers, thermoplastic elastomers, polycarbonates, silicones, andcombinations thereof. In some instances, first coarse fiber layer 65and/or second coarse fiber layer 70 may not be joined to fibrous layer75 by a calendering process. In some such cases, first coarse fiberlayer 65 and/or second coarse fiber layer 70 may not undergo acalendering process. For example, first coarse fiber layer 65 and/orsecond coarse fiber layer 70, in protective clothing material 60, may beuncalendered. In certain embodiments, fibrous layer 75 may be acalendered layer. In some such cases, fibrous layer 75 may be acalendered layer and first coarse fiber layer 65 and/or second coarsefiber layer 70 may be uncalendered layers. Protective coating materialshaving such constructions may have particularly beneficial properties.

In some embodiments, the protective clothing material may include one ormore nonwoven webs or layers (e.g., coarse fiber layer, fibrous layer)having a portion (e.g., surface, interior, all) that repels a fluid(e.g., hydrophilic fluid, aqueous fluid, bodily fluid). In such cases,the nonwoven web or layer may substantially block the transport ofdroplets of the fluid across the protective clothing material. Forexample, the coarse fiber layer may repel fluid droplets (e.g., aqueousfluids, bodily fluids, hydrophilic fluids). As another example, thecoarse fiber layer may repel droplets of a certain size and the fibrouslayer may repel fluid droplets that are not repelled and/or removed bythe coarse fiber layer. For instance, the fibrous layer may be designedto repel smaller droplets that bypass the coarse fibrous layer. Incertain embodiments, the protective clothing material includes one ormore nonwoven webs or layers (e.g., coarse fiber layer, fibrous layer)having a portion (e.g., surface, interior, all) that repels ahydrophilic fluid (e.g., aqueous fluid, bodily fluid). In some suchembodiments, at least a portion of the nonwoven web or layer may behydrophobic. For instance, the nonwoven web may comprise fibers formedfrom a hydrophobic material (e.g., polypropylene) and/or may be modifiedwith a hydrophobic material.

In some embodiments, as described in more detail below, the protectiveclothing material may include one or more modified nonwoven webs orlayers (e.g., surface modified fibrous layer, surface modified coarselayer, surface modified nonwoven web). In some such embodiments, atleast a portion of the nonwoven web or layer (e.g., surface, interior,substantially all, entire) may be modified to repel a fluid (e.g.,aqueous fluid, bodily fluid). For instance, the nonwoven web or layermay be modified to alter and/or reduce the wettability of at least aportion of the nonwoven web or layer (e.g., at least one surface of alayer) with respect to a particular fluid (e.g., to make a layer ornonwoven web more hydrophobic). For example, a hydrophobic surfacehaving a water contact angle of 100° may be modified to have a watercontact angle of greater than 100°, such as 130° or greater. In anotherexample, a hydrophobic surface having a water contact angle of 100° maybe modified to have a water contact angle of 150° or greater. In someembodiments, a surface with a contact angle greater than or equal to150° C. may be referred to as a “superhydrophobic surface.” Asuperhydrophobic surface may also have a low hysteresis of the contactangle.

As used herein, the terms “repel” and “repelling” may refer to theability of a fluid to interact with the nonwoven web or layer, such thatthe contact angle of the fluid with respect to at least a portion (e.g.,surface) of the nonwoven web or layer is greater than or equal to 90degrees. As used herein, the terms “wettability” may refer to theability of a fluid to interact with the nonwoven web or layer, such thatthe contact angle of the fluid with respect to at least a portion (e.g.,surface) of the nonwoven web or layer is less than 90 degrees.

Non-limiting examples of a modified nonwoven web and layer are shown inFIGS. 5A-B. As shown illustratively in FIG. 5A, at least a portion of anonwoven web 100 (e.g., surface(s) and/or interior, entire nonwoven web)may be modified with a material 105. In some embodiments, at least aportion of the surface(s) of the nonwoven web (e.g., in the fibrouslayer) may be modified with a material. For example, the nonwoven webmay have one or more surfaces (e.g., outermost surface with respect tothe protective clothing material, two opposing surfaces, the top surfaceand the bottom surface) modified with a material. In some cases, atleast a portion of the interior of the nonwoven web may be modified witha material. In certain embodiments, at least a portion of the surface(s)and interior of the nonwoven web may be modified with a material. Insome embodiments, the entire nonwoven web may be modified.

In some embodiments, as shown illustratively in FIG. 5B, at least aportion of a layer 110 (e.g., surface(s) and/or interior, entire layer)may be modified with a material 115. In some embodiments, at least aportion of the surface(s) of the layer (e.g., coarse fiber layer) may bemodified with a material as illustrated in FIG. 5B. In certainembodiments, layer 110 may have two or more surfaces (e.g., two opposingsurfaces, the top surface and the bottom surface) modified with amaterial. In other embodiments, layer 110 may have one surface (e.g.,outermost surface with respect to the protective clothing material)modified with a material. In some cases, at least a portion of theinterior of the layer may be modified with a material. In certainembodiments, at least a portion of the surface(s) and interior of thelayer may be modified with a material In some embodiments, the entirelayer may be modified.

In general, any suitable nonwoven web or layer in the protectiveclothing material may be a modified nonwoven web or layer. In someembodiments, the protective clothing material may comprise a singlemodified layer or nonwoven web. In some embodiments, each layer in theprotective clothing material may be a modified layer. In certainembodiments, each nonwoven web in the protective clothing material maybe a modified nonwoven web. In some embodiments, less than or equal totwo nonwoven webs or layers in a protective clothing material may bemodified. In some embodiments, the protective clothing material does notcomprise a modified layer and/or nonwoven web.

As described herein, at least a portion of a nonwoven web or layer maybe modified with a material. In certain embodiments, only a singlesurface of the nonwoven web or layer is modified with a material. Insome instances, opposing surfaces of the nonwoven web or layer aremodified with a material. In some cases, only the interior of thenonwoven web or layer is modified with a material. In some embodiments,the entire nonwoven web or layer may be modified with a material. Ingeneral, a modified layer or nonwoven web comprises a material on atleast a portion of the fibers (e.g., at the surface, in the interior).In some cases, the material may form a coating on at least a portion ofthe fibers (e.g., at the surface, in the interior) of the layer ornonwoven web. In some embodiments, the material is not a binder resin ora portion of a multicomponent fiber.

In some embodiments, one or more nonwoven webs or layers in theprotective clothing material may be designed to be discrete from anothernonwoven web or layer. That is, the fibers from one nonwoven web orlayer do not substantially intermingle (e.g., do not intermingle at all)with fibers from another nonwoven web or layer. For example, withrespect to FIG. 1, in one set of embodiments, fibers from the firstnonwoven web do not substantially intermingle with fibers of the secondnonwoven web. As another example, fibers from the fibrous layer do notsubstantially intermingle with fibers of the optional coarse fiberlayer. Discrete nonwoven webs and/or layers may be joined by anysuitable process, such as calendering or by adhesives. For instance, insome embodiments, discrete nonwoven webs in the fibrous layer may bejoined by calendering, as described in more detail below. In some suchcases, a discrete fibrous layer may be joined to the optional coarsefiber layer(s) using adhesives. It should be appreciated, however, thatcertain embodiments may include one or more nonwoven webs or layers thatare not discrete with respect to one another.

It should be understood that the configurations of the nonwoven websand/or layers shown in the figures are by way of example only, and thatin other embodiments, protective clothing materials including otherconfigurations of nonwoven webs and/or layers may be possible. Forexample, while the first, optional second, and optional third nonwovenwebs are shown in a specific order in FIG. 4, other configurations arealso possible. For example, the optional second nonwoven web may bepositioned between the first and third nonwoven webs. It should beappreciated that the terms “second” and “third” nonwoven webs or layers,as used herein, refer to different nonwoven webs or layers within thematerial, and are not meant to be limiting with respect to the locationof that layer. Furthermore, in some embodiments, additional nonwovenwebs or layers (e.g., “fourth”, “fifth”, “sixth”, or “seventh” layers)may be present in addition to the ones shown in the figures. It shouldalso be appreciated that not all components shown in the figures need bepresent in some embodiments.

As noted above, the fibrous layer may have a relatively small pore size.For instance, in some embodiments, the mean flow pore size of thefibrous layer may be less than or equal to about 6 microns, less than orequal to about 5.5 microns, less than or equal to about 5 microns, lessthan or equal to about 4.5 microns, less than or equal to about 4microns, less than or equal to about 3.5 microns, less than or equal toabout 3 microns, less than or equal to about 2.5 microns, less than orequal to about 2 microns, or less than or equal to about 1.5 microns. Insome instances, the mean flow pore size may be greater than or equal toabout 1 micron, greater than or equal to about 1.5 microns, greater thanor equal to about 2 microns, greater than or equal to about 2.5 microns,greater than or equal to about 3 microns, greater than or equal to about3.5 microns, greater than or equal to about 4 microns, greater than orequal to about 4.5 microns, greater than or equal to about 5 microns, orgreater than or equal to about 5.5 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 1 micron and less than or equal to about 6 microns, greaterthan or equal to about 2 microns and less than or equal to about 5microns). The mean flow pore size may be determined according to thestandard ASTM F316-03 (2011)

In some embodiments, the fibrous layer may have a relatively uniformmean flow pore size. For example, the standard deviation in mean flowpore size when measured across the fibrous layer may be relativelysmall. For instance, in some embodiments, the standard deviation in meanflow pore size when measured across the fibrous layer may be less thanor equal to about 2 microns, less than or equal to about 1.8 microns,less than or equal to about 1.6 microns, less than or equal to about 1.4microns, less than or equal to about 1.2 microns, less than or equal toabout 1 micron, less than or equal to about 0.8 microns, less than orequal to about 0.6 microns, less than or equal to about 0.4 microns,less than or equal to about 0.2 microns, or less than or equal to about0.1 microns. In some instances, the standard deviation in mean flow poresize may be greater than or equal to about 0 microns, greater than orequal to about 0.2 micron, greater than or equal to about 0.4 microns,greater than or equal to about 0.6 microns, greater than or equal toabout 0.8 microns, greater than or equal to about 1 micron, greater thanor equal to 1.2 about microns, greater than or equal to about 1.4microns, greater than or equal to about 1.6 microns, or greater than orequal to about 1.8 microns. Combinations of the above-referenced rangesare also possible (e.g., greater than or equal to about 0 microns andless than or equal to about 2 microns, greater than or equal to about 0micron and less than or equal to about 1 micron). The standard deviationin mean flow pore size may be determined according to the standard ASTMF316-03 (2011). Briefly, the mean flow pore size may be taken atregularly spaced intervals (e.g., 7 inches apart) along the width of thematerial. The standard deviation is determined from a statisticallysignificant number of samples. For example, to determine the standarddeviation of a fibrous layer and/or protective clothing material havingan area of 1 m², a width of 2 m, and a length of 0.5 m, the mean flowpore size is measured at 12 locations along the width of the layer ormaterial. The first measurement is taken 4 inches from an edge of thelayer or material that is used to determine the width and the lastmeasurement is taken 4 inches from the other edge used to determine thewidth. The remaining measurements are spaced across the width, such thatthe 12 measurements are approximately equidistant apart. The standarddeviation is calculated using methods known to those of ordinary skillin the art.

In some embodiments, the maximum pore size of the fibrous layer may berelatively small. For instance, in some embodiments, the maximum poresize of the fibrous layer may be greater than or equal to about 4microns, greater than or equal to about 5 microns, greater than or equalto about 6 microns, greater than or equal to about 7 microns, greaterthan or equal to about 8 microns, greater than or equal to about 9microns, greater than or equal to about 10 microns, or greater than orequal to about 11 microns. In some instances, the maximum pore size ofthe fibrous layer may be less than or equal to about 12 microns, lessthan or equal to about 11 microns, less than or equal to about 10microns, less than or equal to about 9 microns, less than or equal toabout 8 microns, less than or equal to about 7 microns, less than orequal to about 6 microns, or less than or equal to about 5 microns.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 4 microns and less than or equal to about12 microns, greater than or equal to about 6 microns and less than orequal to about 9 microns). The maximum pore size may be determinedaccording to the standard ASTM F316-03 (2011).

In some embodiments, the ratio of mean flow pore size to maximum poresize of the fibrous layer may be greater than or equal to about 0.1,greater than or equal to about 0.2, greater than or equal to about 0.35,greater than or equal to about 0.4, greater than or equal to about 0.5,greater than or equal to about 0.6, greater than or equal to about 0.7,greater than or equal to about 0.8, or greater than or equal to about0.9. In some instances, the ratio of a mean flow pore size to a maximumpore size may be less than or equal to about 1.0, less than or equal toabout 0.9, less than or equal to about 0.8, less than or equal to about0.7, less than or equal to about 0.6, less than or equal to about 0.55,less than or equal to about 0.4, less than or equal to about 0.3, orless than or equal to about 0.2. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to about 0.1 andless than or equal to about 1.0, or greater than or equal to about 0.35and less than or equal to about 0.55). The ratio may be determinedaccording to the standard ASTM F316-03 (2011).

In some embodiments, the difference between the mean flow pore size andthe maximum pore size may be relatively small. For instance, in someembodiments, the difference between the mean flow pore size and themaximum pore size may be less than or equal to about 10 microns, lessthan or equal to about 9 microns, less than or equal to about 8 microns,less than or equal to about 7 microns, less than or equal to about 6microns, less than or equal to about 5 microns, less than or equal toabout 4 microns, less than or equal to about 3 microns, less than orequal to about 2 microns, or less than or equal to about 1 micron. Insome instances, the difference may be greater than or equal to about 0microns, greater than or equal to about 1 micron, greater than or equalto about 2 microns, greater than or equal to about 3 microns, greaterthan or equal to about 4 microns, greater than or equal to about 5microns, greater than or equal to about 6 microns, greater than or equalto about 7 microns, greater than or equal to about 8 microns, or greaterthan or equal to about 9 microns. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to about 0 micronand less than or equal to about 10 microns, greater than or equal toabout 0 microns and less than or equal to about 6 microns).

In some embodiments, the fibrous layer may have a relatively high airpermeability. For instance, in some embodiments, the fibrous layer mayhave an air permeability of greater than or equal to about 1 ft³/min(CFM), greater than or equal to about 2 CFM, greater than or equal toabout 3 CFM, greater than or equal to about 4 CFM, greater than or equalto about 5 CFM, greater than or equal to about 6 CFM, greater than orequal to about 7 CFM, greater than or equal to about 8 CFM, or greaterthan or equal to about 9 CFM. In some instances, the air permeability ofthe fibrous layer may be less than or equal to 10 CFM, less than orequal to 9 CFM, less than or equal to 8 CFM, less than or equal to 7CFM, less than or equal to 6 CFM, less than or equal to 5 CFM, less thanor equal to 4 CFM, less than or equal to 3 CFM, or less than or equal to2 CFM. Combinations of the above-referenced ranges are also possible(e.g., greater than 1 CFM and less than or equal to 10 CFM, greater than4 CFM and less than or equal to 10 CFM, greater than 4 CFM and less thanor equal to 7 CFM). Other ranges are also possible. The air permeabilitymay be determined using ASTM D737 (2016).

In some embodiments, the fibrous layer may have a relatively uniform airpermeability. For example, the standard deviation in air permeabiltywhen measured across the fibrous layer may be relatively small. Forinstance, in some embodiments, the standard deviation in air permeabiltywhen measured across the fibrous layer may be less than or equal toabout 2 CFM, less than or equal to about 1.8 CFM, less than or equal toabout 1.6 CFM, less than or equal to about 1.5 CFM, less than or equalto about 1.3 CFM, less than or equal to about 1 CFM, less than or equalto about 0.8 CFM, less than or equal to about 0.6 CFM, less than orequal to about 0.5 CFM, less than or equal to about 0.3 CFM, or lessthan or equal to about 0.1 CFM. In some instances, the standarddeviation in air permeabilty may be greater than or equal to about 0CFM, greater than or equal to about 0.3 CFM, greater than or equal toabout 0.5 CFM, greater than or equal to about 0.6 CFM, greater than orequal to about 0.8 CFM, greater than or equal to about 1 CFM, greaterthan or equal to 1.3 about CFM, greater than or equal to about 1.5 CFM,greater than or equal to about 1.6 CFM, or greater than or equal toabout 1.8 CFM. Combinations of the above-referenced ranges are alsopossible (e.g., greater than or equal to about 0 CFM and less than orequal to about 2 CFM, greater than or equal to about 0 CFM and less thanor equal to about 1 CFM). The standard deviation in air permeabilty maybe determined according to the standard ASTM D737 (2016). Briefly, themean flow pore size may be taken at regularly spaced intervals (e.g., 7inches apart) along the width of the material. The standard deviation isdetermined from a statistically significant number of samples. Forexample, to determine the standard deviation of a fibrous layer and/orprotective clothing material having an area of 1 m², a width of 2 m, anda length of 0.5 m, the mean flow pore size is measured at 12 locationsalong the width of the layer or material. The first measurement is taken4 inches from an edge of the layer or material that is used to determinethe width and the last measurement is taken 4 inches from the other edgeused to determine the width. The remaining measurements are spacedacross the width, such that the 12 measurements are approximatelyequidistant apart. The standard deviation is calculated using methodsknown to those of ordinary skill in the art.

In some embodiments, the fibrous layer may be relatively lightweight.For instance, in some embodiments, the fibrous layer for filtration mayhave a basis weight of less than or equal to about 50 g/m², less than orequal to about 45 g/m², less than or equal to about 40 g/m², less thanor equal to about 35 g/m², less than or equal to about 30 g/m², lessthan or equal to about 25 g/m², less than or equal to about 20 g/m², orless than or equal to about 15 g/m². In some instances, the fibrouslayer may have a basis weight of greater than or equal to about 10 g/m²,greater than or equal to about 15 g/m², greater than or equal to about20 g/m², greater than or equal to about 25 g/m², greater than or equalto about 30 g/m², greater than or equal to about 35 g/m², greater thanor equal to about 40 g/m², or greater than or equal to about 45 g/m².Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 10 g/m² and less than or equal to about50 g/m², greater than or equal to about 20 g/m² and less than or equalto about 40 g/m²). The basis weight may be determined according to thestandard ASTM D3776 (2013).

In some embodiments, the fibrous layer may be relatively thin. Forinstance, in some embodiments, the thickness of the fibrous layer may beless than or equal to about 6 mils, less than or equal to about 5.5mils, less than or equal to about 5 mils, less than or equal to about4.5 mils, less than or equal to about 4 mils, less than or equal toabout 3.5 mils, less than or equal to about 3 mils, less than or equalto about 2.5 mils, less than or equal to about 2 mils, or less than orequal to about 1.5 mils. In some instances, the thickness of the fibrouslayer may be greater than or equal to about 1 mils, greater than orequal to about 1.5 mils, greater than or equal to about 2 mils, greaterthan or equal to about 2.5 mils, greater than or equal to about 3 mils,greater than or equal to about 3.5 mils, greater than or equal to about4 mils, greater than or equal to about 4.5 mils, greater than or equalto about 5 mils, or greater than or equal to about 5.5 mils.Combinations of the above referenced ranges are also possible (e.g.,greater than or equal to about 1 mils and less than or equal to about 6mils, greater than or equal to about 2 mils and less than or equal toabout 4 mils). The thickness may be determined according to the standardASTM D1777 (2015) at 2.6 psi.

In some embodiments, the fibrous layer may be relatively breathable. Forinstance, in some embodiments, the fibrous layer may have a moisturevapor transmission rate of greater than or equal to about 100 g/m²day,greater than or equal to about 500 g/m²day, greater than or equal toabout 1000 g/m²day, greater than or equal to about 2000 g/m²day, greaterthan or equal to about 3000 g/m²day, or greater than or equal to about4000 g/m²day. In some embodiments, the fibrous layer may have a moisturevapor transmission rate of less than or equal to about 5000 g/m²day,less than or equal to about 4000 g/m²day, less than or equal to about3000 g/m²day, less than or equal to about 2000 g/m²day, less than orequal to about 1000 g/m²day, or less than or equal to about 500 g/m²day.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 100 g/m²day and less than or equal toabout 5000 g/m²day, or greater than or equal to about 1000 g/m²day andless than or equal to about 3000 g/m²day). The moisture vaportransmission rate may be determined according to the standard ASTME96-16 (2016).

In some embodiments, fibrous layer and/or one or more nonwoven webswithin the fibrous layer may comprise fibers having a relatively smallaverage fiber diameter. For instance, in some embodiments, the averagefiber diameter of the fibrous layer and/or one or more nonwoven webswithin the fibrous layer may be less than or equal to about 10 microns,less than or equal to about 9 microns, less than or equal to about 8microns, less than or equal to about 7 microns, less than or equal toabout 6 microns, less than or equal to about 5 microns, less than orequal to about 4 microns, less than or equal to about 3 microns, lessthan or equal to about 2 microns, less than or equal to about 1.5microns, less than or equal to about 1.0 microns, less than or equal toabout 0.5 microns, or less than or equal to about 0.1 microns. In someinstances, the average fiber diameter may be greater than or equal toabout 0.01 microns, greater than or equal to about 0.05 microns, greaterthan or equal to about 0.10 microns, greater than or equal to about 0.2microns, greater than or equal to about 0.5 microns, greater than orequal to about 0.7 microns, greater than or equal to about 1 micron,greater than or equal to about 2 microns, greater than or equal to about3 microns, greater than or equal to about 4 microns, greater than orequal to about 5 microns, greater than or equal to about 6 microns,greater than or equal to about 7 microns, greater than or equal to about8 microns, or greater than or equal to about 9 microns. Combinations ofthe above-referenced ranges are also possible (e.g., greater than orequal to about 0.01 microns and less than or equal to about 10 microns,greater than or equal to about 0.1 microns and less than or equal toabout 10 microns, greater than or equal to about 0.05 microns and lessthan or equal to about 1.5 microns). In some embodiments, in which thefibrous layer comprises an electrospun nonwoven web, the average fiberdiameter of the electrospun nonwoven web may be greater than or equal toabout 0.01 microns and less than or equal to about 0.05 microns. Theaverage fiber diameter may be determined using scanning electronmicroscopy. As used herein, fiber diameter refers to the largestcross-sectional dimension of the fiber from a cross-sectionperpendicular to the axis corresponding to the fiber length.

As described herein, in some embodiments, a protective clothing materialmay comprise one or more coarse fiber layers. For instance, theprotective clothing material may comprise a fibrous layer positionedbetween and optionally adjacent to two coarse fiber layers. In someembodiments, the coarse fiber layer may be a relatively open layer thatimparts splash resistance, breathability, and good air permeability tothe protective clothing material. For instance, the coarse layer mayprevent the transmission of low pressure liquids (e.g., spray of liquid,saliva). In some such embodiments, the coarse layer may repelhydrophilic fluids (e.g., bodily fluids). In some embodiments, thecoarse layer may have a pore size and fiber diameter that impartbreathability and good air permeability to the layer.

In some embodiments, the coarse fiber layer may be splash resistant. Asused herein, the terms “splash resistant” (also referred to as sprayimpact resistant) and “splash resistance” (also referred to as sprayimpact resistance) have their ordinary meaning in the art and may referto the ability of the layer to resist penetration of sprayed fluid. Insome embodiments, the splash resistance of a layer and/or the protectiveclothing material may be determined using AATCC 42, which measures theresistance to the penetration of water by impact. Briefly, a 500 mL ofdeionized water is sprayed against a taut surface of a test specimenbacked by a pre-weighed blotter using 2″ diameter spray head having 25holes at a height of 0.6 m. The test specimen backed by the pre-weighedblotter is angled at 45 degrees. The blotter is then reweighed todetermine water penetration and the specimen is classified accordingly.If the difference in weight is less than 1.0 g, the specimen is splashresistant. In some embodiments, the difference in weight, according tothis test, of the coarse fiber layer, fibrous layer, and/or protectiveclothing material may be less than 1.0 g (e.g., less than 0.8 g, lessthan 0.6 g, less than 0.3 g)

In some embodiments, the air permeability of the coarse fiber layer(s)may be greater than or equal to about 10 ft³/min (CFM), greater than orequal to about 100 CFM, greater than or equal to about 250 CFM, greaterthan or equal to about 500 CFM, greater than or equal to about 750 CFM,greater than or equal to about 1000 CFM, greater than or equal to about1250 CFM, greater than or equal to about 1500 CFM, or greater than orequal to about 1750 CFM. In some instances, the air permeability may beless than or equal to about 2000 CFM, less than or equal to about 1750CFM, less than or equal to about 1500 CFM, less than or equal to about1250 CFM, less than or equal to about 1000 CFM, less than or equal toabout 750 CFM, less than or equal to about 500 CFM, less than or equalto about 250 CFM, or less than or equal to about 100 CFM. Combinationsof the above-referenced ranges are also possible (e.g., greater than orequal to about 10 CFM and less than or equal to about 2000 CFM, greaterthan or equal to about 500 CFM and less than or equal to about 1000CFM). The air permeability may be determined using ASTM D737 (2016).

In some embodiments, the coarse fiber layer(s) may have a relativelylarge pore size that contributes to the breathability and permeabilityof the protective clothing material. For instance, in some embodiments,the mean flow pore size of the coarse fiber layer(s) may be greater thanor equal to about 100 microns, greater than or equal to about 200microns, greater than or equal to about 300 microns, greater than orequal to about 400 microns, greater than or equal to about 500 microns,greater than or equal to about 600 microns, greater than or equal toabout 700 microns, greater than or equal to about 800 microns, orgreater than or equal to about 900 microns. In some instances, the meanflow pore size may be less than or equal to about 1000 microns, lessthan or equal to about 900 microns, less than or equal to about 800microns, less than or equal to about 700 microns, less than or equal toabout 600 microns, less than or equal to about 500 microns, less than orequal to about 400 microns, less than or equal to about 300 microns, orless than or equal to about 200 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 100 microns and less than or equal to about 1000 microns,greater than or equal to about 400 microns and less than or equal toabout 700 microns). The mean flow pore size may be determined accordingto the standard ASTM F316-03 (2011).

In some embodiments, the maximum pore size of the coarse fiber layer(s)may be greater than or equal to about 200 microns, greater than or equalto about 300 microns, greater than or equal to about 500 microns,greater than or equal to about 700 microns, greater than or equal toabout 900 microns, greater than or equal to about 1000 microns, greaterthan or equal to about 1200 microns, greater than or equal to about 1400microns, or greater than or equal to about 1600 microns. In someinstances, the maximum pore size may be less than or equal to about 1800microns, less than or equal to about 1600 microns, less than or equal toabout 1400 microns, less than or equal to about 1200 microns, less thanor equal to about 1000 microns, less than or equal to about 900 microns,less than or equal to about 700 microns, less than or equal to about 500microns, or less than or equal to about 300 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 200 microns and less than or equal to about 1800 microns,greater than or equal to about 500 microns and less than or equal toabout 900 microns). The mean flow pore size may be determined accordingto the standard ASTM F316-03 (2011).

In some embodiments, the ratio of a mean flow pore size to a maximumpore size of the coarse fiber layer(s) may be greater than or equal toabout 0.1, greater than or equal to about 0.2, greater than or equal toabout 0.3, greater than or equal to about 0.4, greater than or equal toabout 0.5, greater than or equal to about 0.6, greater than or equal toabout 0.7, greater than or equal to about 0.8, or greater than or equalto about 0.9. In some embodiments, the ratio of mean flow pore size tothe maximum pore size may be less than or equal to about 1.0, less thanor equal to about 0.9, less than or equal to about 0.8, less than orequal to about 0.7, less than or equal to about 0.6, less than or equalto about 0.5, less than or equal to about 0.4, less than or equal toabout 0.3, or less than or equal to about 0.2. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 0.1 and less than or equal to about 1.0, greater than or equalto about 0.5 and less than or equal to about 0.9). The ratio may bedetermined according to the standard ASTM F316-03 (2011).

In some embodiments, the coarse fiber layer(s) may comprise fibershaving a relatively large fiber diameter that contribute to thebreathability of the protective clothing material. For instance, in someembodiments, the average fiber diameter of the coarse fiber layer(s) maybe greater than or equal to about 10 microns, greater than or equal toabout 15 microns, greater than or equal to about 18 microns, greaterthan or equal to about 20 microns, greater than or equal to about 24microns, greater than or equal to about 27 microns, greater than orequal to about 30 microns, greater than or equal to about 35 microns,greater than or equal to about 40 microns, or greater than or equal toabout 45 microns. In some instances, the average fiber diameter may beless than or equal to about 50 microns, less than or equal to about 45microns, less than or equal to about 40 microns, less than or equal toabout 35 microns, less than or equal to about 30 microns, less than orequal to about 27 microns, less than or equal to about 24 microns, lessthan or equal to about 21 microns, or less than or equal to about 18microns. Combinations of the above-referenced ranges are also possible(e.g., greater than or equal to about 10 microns and less than or equalto about 50 microns, greater than or equal to about 15 microns and lessthan or equal to about 30 microns).

In some embodiments, the coarse fiber layer(s) may have a basis weightof greater than or equal to about 5 g/m², greater than or equal to about10 g/m², greater than or equal to about 15 g/m², greater than or equalto about 20 g/m², greater than or equal to about 25 g/m², greater thanor equal to about 30 g/m², greater than or equal to about 35 g/m²,greater than or equal to about 40 g/m², greater than or equal to about45 g/m², greater than or equal to about 50 g/m², greater than or equalto about 55 g/m², greater than or equal to about 60 g/m², greater thanor equal to about 65 g/m², greater than or equal to about 70 g/m²,greater than or equal to about 75 g/m², greater than or equal to about80 g/m², or greater than or equal to about 90 g/m². In some instances,the basis weight may be less than or equal to about 100 g/m², less thanor equal to about 90 g/m², less than or equal to about 80 g/m², lessthan or equal to about 75 g/m², less than or equal to about 70 g/m²,less than or equal to about 65 g/m², less than or equal to about 60g/m², less than or equal to about 55 g/m², less than or equal to about50 g/m², less than or equal to about 45 g/m², less than or equal toabout 40 g/m², less than or equal to about 35 g/m², less than or equalto about 30 g/m², less than or equal to about 25 g/m², or less than orequal to about 20 g/m². Combinations of the above-referenced ranges arealso possible (e.g., greater than or equal to about 5 g/m² and less thanor equal to about 100 g/m², greater than or equal to about 15 g/m² andless than or equal to about 35 g/m²).

As described herein, protective clothing material comprising a fibrouslayer and optionally one or more coarse fiber layers may be particularlyuseful for a wide variety of applications, including the formation ofANSI/AAMI level 4 protective garments (e.g., surgical gowns, surgicalhoods). In some embodiments, the protective clothing material may havethe requisite protection rating and good wearability (e.g., comfort).For instance, in some embodiments, the protective clothing materialand/or the fibrous layer may pass the ASTM F1671-13 Method B (i.e.,viral penetration) and ASTM F1670-08(2014) el Method (i.e., syntheticblood penetration) test required for ANSI/AAMI level 4 certification.

In addition to a high protection rating, the protective clothingmaterial may also have a relatively high air permeability. For instance,in some embodiments, the protective clothing material may have an airpermeability of greater than or equal to about 1 CFM, greater than orequal to about 2 CFM, greater than or equal to about 3 CFM, greater thanor equal to about 4 CFM, greater than or equal to about 5 CFM, greaterthan or equal to about 6 CFM, greater than or equal to about 7 CFM,greater than or equal to about 8 CFM, or greater than or equal to about9 CFM. In some instances, the air permeability may be less than or equalto about 10 CFM, less than or equal to about 9 CFM, less than or equalto about 8 CFM, less than or equal to about 7 CFM, less than or equal toabout 6 CFM, less than or equal to about 5 CFM, less than or equal toabout 4 CFM, less than or equal to about 3 CFM, or less than or equal toabout 2 CFM. All combinations of the above-referenced ranges arepossible (e.g., greater than about 1 CFM and less than or equal to about10 CFM, greater than about 4 CFM and less than or equal to about 7 CFM).The air permeability may be determined according to the standard ASTMD737 (2016).

In some embodiments, the protective clothing material may be relativelybreathable. For instance, in some embodiments, the protective clothingmaterial may have a moisture vapor transmission rate of greater than orequal to about 100 g/m²day, greater than or equal to about 500 g/m²day,greater than or equal to about 1000 g/m²day, greater than or equal toabout 2000 g/m²day, greater than or equal to about 3000 g/m²day, orgreater than or equal to about 4000 g/m²day. In some embodiments, theprotective clothing material may have a moisture vapor transmission rateof less than or equal to about 5000 g/m²day, less than or equal to about4000 g/m²day, less than or equal to about 3000 g/m²day, less than orequal to about 2000 g/m²day, less than or equal to about 1000 g/m²day,or less than or equal to about 500 g/m²day. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 100 g/m²day and less than or equal to about 5000 g/m²day, orgreater than or equal to about 1000 g/m²day and less than or equal toabout 3000 g/m²day). The moisture vapor transmission rate may bedetermined according to the standard ASTM E-96-16.

In some embodiments, the protective clothing material may be relativelylightweight. For instance, in some embodiments, the protective clothingmaterial may have a basis weight of greater than or equal to about 10g/m², greater than or equal to about 20 g/m², greater than or equal toabout 30 g/m², greater than or equal to about 40 g/m², greater than orequal to about 50 g/m², greater than or equal to about 60 g/m², greaterthan or equal to about 70 g/m², greater than or equal to about 80 g/m²,or greater than or equal to about 90 g/m². In some instances, theprotective clothing material may have a basis weight of less than orequal to about 100 g/m², less than or equal to about 90 g/m², less thanor equal to about 80 g/m², less than or equal to about 70 g/m², lessthan or equal to about 60 g/m², less than or equal to about 50 g/m²,less than or equal to about 40 g/m², less than or equal to about 30g/m², or less than or equal to about 20 g/m². Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 10 g/m² and less than or equal to about 100 g/m², greater thanor equal to about 40 g/m² and less than or equal to about 70 g/m²). Thebasis weight may be determined according to the standard ASTM D3776(2013).

In some embodiments, the protective clothing material may be relativelythin. For instance, in some embodiments, the thickness of the protectiveclothing material may be less than or equal to about 20 mils, less thanor equal to about 18 mils, less than or equal to about 15 mils, lessthan or equal to about 12 mils, less than or equal to about 10 mils,less than or equal to about 9 mils, less than or equal to about 7 mils,or less than or equal to about 6 mils. In some instances, the thicknessmay be greater than or equal to about 5 mils, greater than or equal toabout 7 mils, greater than or equal to about 9 mils, greater than orequal to about 10 mils, greater than or equal to about 12 mils, greaterthan or equal to about 15 mils, or greater than or equal to about 18mils. Combinations of the above referenced ranges are also possible(e.g., greater than or equal to about 5 mils and less than or equal toabout 20 mils, greater than or equal to about 10 mils and less than orequal to about 15 mils). The thickness may be determined according tothe standard ASTM D1777 (2015) at 2.6 psi.

In some embodiments, the protective clothing material may have arelatively a relatively small mean flow and/or maximum pore sizes. Forinstance, in some embodiments, the protective clothing material has amean flow pore size of less than or equal to about 5 microns, less thanor equal to about 4.5 microns, less than or equal to about 4 microns,less than or equal to about 3.5 microns, less than or equal to about 3microns, less than or equal to about 2.5 microns, less than or equal toabout 2 microns, or less than or equal to about 1.5 microns. In someinstances, the protective clothing material may have a mean flow poresize of greater than or equal to about 1 micron, greater than or equalto about 1.5 microns, greater than or equal to about 2 microns, greaterthan or equal to about 2.5 microns, greater than or equal to about 3microns, greater than or equal to about 3.5 microns, greater than orequal to about 4 microns, or greater than or equal to about 4.5 microns.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 1 micron and less than or equal to about5 microns, greater than or equal to about 1.5 microns and less than orequal to about 3 microns). The mean flow pore size may be determinedaccording to the standard ASTM F316-03 (2011).

In some embodiments, the protective clothing material has a maximum poresize of less than or equal to about 10 microns, less than or equal toabout 9 microns, less than or equal to about 8 microns, less than orequal to about 7 microns, less than or equal to about 6 microns, lessthan or equal to about 5 microns, less than or equal to about 4 microns,or less than or equal to about 3 microns. In some instances, theprotective clothing material may have a maximum pore size of greaterthan or equal to about 2 microns, greater than or equal to about 3microns, greater than or equal to about 4 microns, greater than or equalto about 5 microns, greater than or equal to about 6 microns, greaterthan or equal to about 7 microns, greater than or equal to about 8microns, or greater than or equal to about 9 microns. Combinations ofthe above-referenced ranges are also possible (e.g., greater than orequal to about 2 microns and less than or equal to about 10 microns,greater than or equal to about 4 microns and less than or equal to about7 microns). The mean flow pore size may be determined according to thestandard ASTM F316-03 (2011).

In some embodiments, the protective clothing material may have asuitable Mullen Burst strength for use in a protective garment. Forinstance, in some embodiments, protective clothing material may have aMullen Burst strength of greater than or equal to about 30 psi, greaterthan or equal to about 35 psi, greater than or equal to about 40 psi,greater than or equal to about 45 psi, greater than or equal to about 50psi, or greater than or equal to about 55 psi. In some instances, theMullen Burst strength may be less than or equal to about 60 psi, lessthan or equal to about 55 psi, less than or equal to about 50 psi, lessthan or equal to about 45 psi, less than or equal to about 40 psi, orless than or equal to about 35 psi. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to about 30 psiand less than or equal to about 60 psi). The Mullen Burst strength maybe determined according to the standard ASTM D774 (2010).

In some embodiments, the hydrostatic pressure or hydrostatic head rangeof the protective clothing material and/or the fibrous layer may berelatively high (e.g., greater than or equal to about 100 cm H₂O). Forinstance, in some embodiments, the hydrostatic pressure or hydrostatichead range of the protective clothing material and/or the fibrous layermay greater than or equal to about 50 cm H₂O, greater than or equal toabout 75 cm H₂O, greater than or equal to about 100 cm H₂O, greater thanor equal to about 125 cm H₂O, greater than or equal to about 150 cm H₂O,greater than or equal to about 175 cm H₂O, greater than or equal toabout 200 cm H₂O, greater than or equal to about 225 cm H₂O, greaterthan or equal to about 250 cm H₂O, or greater than or equal to about 275cm H₂O. In some instances, the hydrostatic pressure or hydrostatic headrange may be less than or equal to about 300 cm H₂O, less than or equalto about 275 cm H₂O, less than or equal to about 250 cm H₂O, less thanor equal to about 225 cm H₂O, less than or equal to about 200 cm H₂O,less than or equal to about 175 cm H₂O, less than or equal to about 150cm H₂O, less than or equal to about 125 cm H₂O, or less than or equal toabout 100 cm H₂O. Combinations of the above-referenced ranges arepossible (e.g., greater than or equal to about 50 cm H₂O and less thanor equal to about 300 cm H₂O, greater than or equal to about 100 cm H₂Oand less than or equal to about 200 cm H₂O)

In some embodiments, the weight percentage of the fibrous layer in theprotective clothing material may be greater than or equal to about 1%,greater than or equal to about 10%, greater than or equal to about 20%,greater than or equal to about 30%, greater than or equal to about 40%,greater than or equal to about 50%, greater than or equal to about 60%,greater than or equal to about 70%, or greater than or equal to about80%. In some instances, the weight percentage of the fibrous layer inthe protective clothing material may be less than or equal to about 99%,less than or equal to about 80%, less than or equal to about 70%, lessthan or equal to about 60%, less than or equal to about 50%, less thanor equal to about 40%, less than or equal to about 30%, less than orequal to about 20%, or less than or equal to about 10%. Combinations ofthe above-referenced ranges are also possible (e.g., greater than orequal to about 1% and less than or equal to about 99%, greater than orequal to about 40% and less than or equal to about 60%).

In some embodiments, the weight percentage of the coarse fiber layer(s)in the protective clothing material may be greater than or equal toabout 1%, greater than or equal to about 10%, greater than or equal toabout 20%, greater than or equal to about 30%, greater than or equal toabout 40%, greater than or equal to about 50%, greater than or equal toabout 60%, greater than or equal to about 70%, or greater than or equalto about 80%. In some instances, the weight percentage of the coarsefiber layer(s) in the protective clothing material may be less than orequal to about 99%, less than or equal to about 80%, less than or equalto about 70%, less than or equal to about 60%, less than or equal toabout 50%, less than or equal to about 40%, less than or equal to about30%, less than or equal to about 20%, or less than or equal to about10%. Combinations of the above-referenced ranges are also possible(e.g., greater than or equal to about 1% and less than or equal to about99%, greater than or equal to about 40% and less than or equal to about60%).

In general, the contact angle of one or more nonwoven webs, one or morelayers (e.g., coarse fiber layer), and/or the protective clothingmaterial may be selected to repel a fluid (e.g., hydrophilic fluid). Insome embodiments, the water contact angle on a surface of one or morenonwoven webs, one or more layers, and/or the protective clothingmaterial may be greater than 90 degrees, greater than or equal to 100degrees, greater than or equal to 105 degrees, greater than or equal to110 degrees, greater than or equal to 115 degrees, greater than or equalto 120 degrees, greater than or equal to 125 degrees, greater than orequal to 130 degrees, greater than or equal to 135 degrees, greater thanor equal to 145 degrees, greater than or equal to 150 degrees, greaterthan or equal to 155 degrees, or greater than or equal to 160 degrees.In some instances, the water contact angle is less than or equal toabout 165 degrees, less than or equal to about 160 degrees, less than orequal to about 150 degrees, less than or equal to about 140 degrees,less than or equal to about 130 degrees, less than or equal to about 120degrees, less than or equal to about 110 degrees, or less than or equalto about 100 degrees. Combinations of the above-referenced ranges arealso possible (e.g., greater than or equal to about 90 degrees and lessthan or equal to about 165 degrees). The water contact angle may bemeasured using standard ASTM D5946 (2009). The contact angle is theangle between the substrate surface and the tangent line drawn to thewater droplet surface at the three-phase point, when a liquid drop isresting on the substrate surface. A contact angle meter or goniometercan be used for this determination.

As described herein, one or more layers (e.g., fibrous layer, coarsefiber layer), one or more nonwoven webs, and/or the protective clothingmaterial may comprise synthetic fibers. In some instances, one or morelayers (e.g., fibrous layer, coarse fiber layer), one or more nonwovenwebs, and/or the entire protective clothing material may comprise arelatively high weight percentage of synthetic fibers (e.g., greaterthan or equal to about 95 wt. %, 100 wt. %). In some instances, thefibrous layer may comprise a relatively high weight percentage ofsynthetic fibers (e.g., greater than or equal to about 95 wt. %, 100 wt.%). In some instances, the synthetic fibers may be continuous (e.g.,greater than about 10 cm, greater than about 50 cm, greater than about200 cm), as described further below. In certain embodiments, one or morenonwoven webs (e.g., first nonwoven web, second nonwoven web) maycomprise a relatively high percentage (e.g., greater than or equal toabout 95 wt. %, 100 wt. %) of synthetic fibers (e.g., meltblown fibers,electrospun fibers). In certain embodiments, one or more coarse fiberlayers (e.g., first coarse fiber layer, second coarse fiber layer) maycomprise a relatively high percentage (e.g., greater than or equal toabout 75 wt. %, greater than or equal to about 95 wt. %, 100 wt. %) ofsynthetic fibers (e.g., synthetic staple fibers).

In some embodiments, the fibers in one or more nonwoven webs, the layers(e.g., fibrous layer), and/or the protective clothing material may becontinuous fibers formed by any suitable process (e.g., a meltblowing, ameltspinning, an electrospinning, centrifugal spinning). In certainembodiments, at least some of the synthetic fibers may be formed by ameltblowing or electrospinning process (e.g., melt electrospinning,solvent electrospinning). In other embodiments, the synthetic fibers maybe non-continuous. In some embodiments, all of the fibers in theprotective clothing material are synthetic fibers. In certainembodiments, all of the fibers in the fibrous layer are syntheticfibers.

In some cases, the synthetic fibers may be continuous (e.g., electrospunfibers, meltblown fibers, spunbond fibers, centrifugal spun fibers,etc.). For instance, synthetic fibers may have an average length of atleast about 10 cm, at least about 15 cm, at least about 20 cm, at leastabout 50 cm, at least about 100 cm, at least about 200 cm, at leastabout 500 cm, at least about 700 cm, at least about 1000 cm, at leastabout 1500 cm, at least about 2000 cm, at least about 2500 cm, at leastabout 5000 cm, at least about 10000 cm; and/or less than or equal toabout 10000 cm, less than or equal to about 5000 cm, less than or equalto about 2500 cm, less than or equal to about 2000 cm, less than orequal to about 1000 cm, less than or equal to about 500 cm, or less thanor equal to about 200 cm. Combinations of the above-referenced rangesare also possible (e.g., greater than or equal to about 100 cm and lessthan or equal to about 2500 cm). Other values of average fiber lengthare also possible.

In other embodiments, the synthetic fibers (e.g., in the coarse fiberlayer(s)) are not continuous (e.g., staple fibers). In general,synthetic non-continuous fibers may be characterized as being shorterthan continuous synthetic fibers. For instance, in some embodiments,synthetic fibers may have an average length of greater than or equal toabout 1 mm, greater than or equal to about 4 mm, greater than or equalto about 6 mm, greater than or equal to about 10 mm, greater than orequal to about 15 mm, greater than or equal to about 20 mm, greater thanor equal to about 25 mm, greater than or equal to about 30 mm, greaterthan or equal to about 35 mm, greater than or equal to about 40 mm,greater than or equal to about 50 mm, greater than or equal to about 60mm, greater than or equal to about 70 mm, greater than or equal to about80 mm, greater than or equal to about 90 mm. In some instances, theaverage length may be less than or equal to about 100 mm, less than orequal to about 80 mm, less than or equal to about 60mm, less than orequal to about 40 mm, less than or equal to about 30 mm, less than orequal to about 20 mm, less than or equal to about 15 mm, or less than orequal to about 10 mm. Combinations of the above-referenced ranges arealso possible (e.g., at least about 1.0 mm and less than or equal toabout 100 mm, at least about 6.0 mm and less than or equal to about 30mm).

In some embodiments in which synthetic fibers are included in theprotective clothing material, the weight percentage of synthetic fibersin one or more layers, one or more nonwoven webs, and/or the protectiveclothing material may be greater than or equal to about 50%, greaterthan or equal to about 60%, greater than or equal to about 75%, greaterthan or equal to about 90%, greater than or equal to about 95%, greaterthan or equal to about 98%, or greater than or equal to about 99%. Insome instances, the weight percentage of synthetic fibers may be lessthan or equal to about 100%, less than or equal to about 99%, less thanor equal to about 98%, less than or equal to about 95%, less than orequal to about 90%, less than or equal to about 80%, or less than orequal to about 70%. Combinations of the above-referenced ranges are alsopossible (e.g., greater than or equal to about 75% and less than orequal to about 100%). In some embodiments, one or more nonwoven webs,one or more layers (e.g., fibrous layer, coarse fiber layer), and/or theprotective clothing material includes 100% synthetic fibers.

Synthetic fibers may include any suitable type of synthetic polymer.Examples of suitable synthetic fibers include polyimide, aliphaticpolyamide (e.g., nylon 6), aromatic polyamide, polysulfone, celluloseacetate, polyether sulfone, polyaryl ether sulfone, modified polysulfonepolymers, modified polyethersulfone polymers, polymethyl methacrylate,polyacrylonitrile, polyurethane, poly(urea urethane), polybenzimidazole,polyetherimide, polyacrylonitrile, poly(ethylene terephthalate),polypropylene, silicon dioxide (silica), regenerated cellulose (e.g.,Lyocell, rayon,) carbon (e.g., derived from the pyrolysis ofpolyacrilonitrile), polyaniline, poly(ethylene oxide), poly(ethylenenaphthalate), poly(butylene terephthalate), styrene butadiene rubber,polystyrene, poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidenefluoride), poly(ethylene-co-vinyl acetate), polyethyleneoxide, chitosan,polyhydroxybutyrate, hydroxyapatite, fiberglass, poly(vinyl butylene)and copolymers or derivative compounds thereof, and combinationsthereof. In some embodiments, the synthetic fibers are hydrophobic. Insome embodiments, the synthetic fibers are organic polymer fibers.Synthetic fibers may also include multi-component fibers (i.e., fibershaving multiple components such as bicomponent fibers). In some cases,synthetic fibers may include electrospun (e.g., melt, solvent),meltblown, meltspun, or centrifugal spun fibers, which may be formed ofpolymers described herein (e.g., polyester, polypropylene). In someembodiments, synthetic fibers may be electrospun fibers. In someembodiments, synthetic fibers may be meltblown fibers. The filter media,as well as each of the fiber webs within the filter media, may alsoinclude combinations of more than one type of synthetic fiber.

In certain embodiments, a protective clothing material comprising two ormore layers including fibers formed from the same or similar materialmay have beneficial properties during seaming and/or at the seams. Forinstance, protective garments formed from a protective clothing materialcomprising two or more layers including fibers formed from the same orsimilar material can be formed using heat sealing and/or ultrasonicseaming. In some cases, protective garments formed from such aprotective clothing material may have seams that have the sameprotection rating as the rest of the garment. Conversely, protectivegarments formed from a protective clothing material comprising two ormore layers including dissimilar material may not be amenable to seamingvia heat sealing and/or ultrasonic seaming. In such cases, thread may beused to join protective clothing material together to form a garment.The seams containing thread may have a lower protection rating than therest of the garment.

In some embodiments, two or more layers in the protective clothingmaterial may comprise fibers formed from the same or similar material(e.g., synthetic polymer). For instance, the fibrous layer may includesynthetic fibers including a certain synthetic polymer (e.g.,polypropylene) and the coarse fiber layer(s) may include syntheticfibers including the same synthetic polymer (polypropylene). As anotherexample, two or more nonwoven webs in the fibrous layer may comprisesynthetic fibers including the same synthetic polymer (e.g.,polypropylene). In some embodiments, the weight percentage of fibers ina layer that include the same or similar material (e.g., syntheticpolymer) as fibers in another layer (e.g., adjacent layer) may berelatively high (e.g., greater than or equal to about 80 wt. %, greaterthan or equal to about 85 wt. %, greater than or equal to about 90 wt.%, greater than or equal to about 95 wt. %, 100 wt. %). In certainembodiments, the weight percentage of fibers in a layer that include adifferent material (e.g., synthetic polymer) than fibers in anotherlayer (e.g., adjacent layer) may be relatively low (e.g., less than orequal to about 20 wt. %, less than or equal to about 15 wt. %, less thanor equal to about 10 wt. %, less than or equal to about 5 wt. %). Insome embodiments, one or more nonwoven webs (e.g., first nonwoven web,second nonwoven web), one or more layers (e.g., coarse fiber layer,fibrous layers) and/or the entire protective clothing material mayinclude a single fiber type (e.g., synthetic fibers). For example, thecoarse fiber layer(s) and fibrous layer may include only polypropylenefibers.

In general, the protective clothing material, and accordingly thefibrous layer and coarse fiber layer, may include any suitable fibertype. For instance, in some embodiments, the coarse fiber layer(s) mayinclude natural fibers (e.g., cotton fibers, cellulose fibers) that are,e.g., comfortable for the wearer. In some such embodiments, one or morecoarse fiber layers may include a blend of synthetic fibers (e.g., rayonfibers, acrylic fibers) and natural fibers (e.g., cotton fibers) Acarded blend of synthetic and natural fibers (like cotton).

Protective clothing materials, described herein, may comprise layersproduced using any suitable processes, such as a non-wet laid or a wetlaid process. In some embodiments, one or more nonwoven webs (e.g., inthe fibrous layer) and/or one or more layers (e.g., coarse fiber layer)may be produced using a non-wet laid process, such as blowing orspinning process. In some embodiments, one or more nonwoven webs (e.g.,in the fibrous layer), one or more layers, and/or the entire protectiveclothing material may be formed by a meltblowing system, such as themeltblown system described in U.S. Publication No. 2009/0120048, filedNov. 7, 2008, and entitled “Meltblown Filter Medium”, and U.S.Publication No. 2012-0152824, filed Dec. 17, 2010, and entitled, “FineFiber Filter Media and Processes”, each of which is incorporated hereinby reference in its entirety for all purposes. In certain embodiments,one or more nonwoven webs and/or one or more layers may be formed by ameltspinning or a centrifugal spinning process.

In some embodiments, the nonwoven webs and/or layers, described herein,may have a relatively low amount of or essentially no process defects.In general, it is believed that subjecting the polymer composition usedto form the fibers in the non-woven web to relatively high temperaturesand pressures for extended periods of time in an extrusion system cancause the polymer composition to degrade. Degradation may involve chainscission, i.e., shortening of the polymer chains to produce lowermolecular weight polymers, and/or other forms of decomposition (e.g.,chemical decomposition, thermal decomposition, ionization). As a resultof polymer degradation, small polymeric particles may be formed. Theseparticles may have the same chemical composition as the polymercomposition used to form the fibers (but having a lower molecularweight), or may be a derivative of the polymer composition used to formthe fibers. The particles may be associated with the nonwoven web invarious configurations. For instance, the particles may reside on thesurface of the fibers, on the surface of the fiber web, in the center ofthe fiber web, or in combinations thereof.

The shape and size of the polymeric particles formed may vary, and insome cases, the particles can even agglomerate to form larger particles.It should be understood that the polymeric particles described hereinare different from fibers. The polymeric particles are non-fibrous, andgenerally have an aspect ratio (i.e., a length to largestcross-sectional dimension) of less than 50:1 and a largestcross-sectional dimension of at least 0.2 mm. For instance, in someembodiments, a particle may have a largest cross-sectional dimension ofless than or equal to about 10 mm, less than or equal to about 8 mm,less than or equal to about 6 mm, less than or equal to about 4 mm, lessthan or equal to about 2 mm, less than or equal to about 1 mm, or lessthan or equal to about 0.5 mm. In some instances, a particle may have alargest cross-sectional dimension of greater than or equal to about 0.2mm, greater than or equal to about 0.5 mm, greater than or equal toabout 1.0 mm, greater than or equal to about 2.0 mm, greater than orequal to about 4.0 mm, greater than or equal to about 6.0 mm, greaterthan or equal to about 8.0 mm. It should be understood that allcombinations of the above-referenced ranges are possible (e.g., greaterthan or equal to about 0.2 mm and less than or equal to about 10 mm).Other values and ranges of particle size are also possible.

In certain embodiments, the number average molecular weight of theparticles formed during a fiber extrusion process may be less than orequal to about ½ the number average molecular weight of the polymer usedto form the fibers. For instance, the number average molecular weight ofthe particles formed during a fiber extrusion process may be less thanor equal to about ⅛, less than or equal to about 1/64, or less than orequal to about 1/200 the number average molecular weight of the polymerused to form the fibers. Other values of molecular weight of theparticles associated with a fiber web are also possible.

In some embodiments, a nonwoven web and/or layer as described herein mayinclude a relatively low number of or essentially no particles (e.g., onits surface). The amount of particles may be measured by determining thesurface density of particles on the nonwoven web, i.e., the number ofparticles on a surface of the nonwoven web per unit area of the nonwovenweb surface. For instance, a nonwoven web and/or layer may have asurface density of particles of less than or equal to about 12.0particles/inch², less than or equal to about 10.0 particles/inch², lessthan or equal to about 8.0 particles/inch², less than or equal to about6.0 particles/inch², less than or equal to about 4.0 particles/inch²,less than or equal to about 2.5 particles/inch², less than or equal toabout 2.2 particles/inch², less than or equal to about 2.0particles/inch², less than or equal to about 1.8 particles/inch², lessthan or equal to about 1.6 particles/inch², less than or equal to about1.5 particles/inch², less than or equal to about 1.3 particles/inch²,less than or equal to about 1.0 particles/inch², less than or equal toabout 0.8 particles/inch², less than or equal to about 0.5particles/inch², or less than or equal to about 0.3 particles/inch²,wherein each of the particles has a largest cross-sectional dimension ofone of the ranges or values described above. For example, in oneparticular embodiment, a nonwoven web and/or layer has a surface densityof particles of less than or equal to about 3.0 particles/inch², whereineach of the particles has a largest cross-sectional dimension of about0.2 mm or greater. In this embodiment, even though the nonwoven web mayinclude some particles having a largest cross-sectional dimensionsmaller than about 0.2 mm, these particles are not accounted for incalculating the surface density of particles. In another embodiment, anonwoven web and/or layer has a surface density of particles of lessthan or equal to about 3.0 particles/inch, wherein each of the particleshas a largest cross-sectional dimension of about 1.0 mm or greater. Inthis embodiment, even though the nonwoven web and/or layer may includesome particles having a largest cross-sectional dimension smaller thanabout 1.0 mm, these particles are not accounted for in calculating thesurface density of particles. Other surface densities of particles in aparticular size range or value are also possible.

The number of particles per unit area of nonwoven web and/or layer canbe determined as follows. A sample of nonwoven web and/or layer can belayered together with carbon paper and a white sheet of standard copypaper, where the carbon paper is positioned between the nonwoven web andthe copy paper. The composite structure can be placed in a continuousbelt press where the following conditions are employed: a line speed of2.5 m/min, a pressure of 6 bars, and a temperature of about 68° F.-80°F. (room temperature). After exposure to these conditions, the degradedpolymer particles, if present, may lie at an elevated position comparedto the fibers, and appear as small “dots” on the underlying copy paper.If a darker image is needed for detection, the copy paper can bephotocopied with a standard copier to darken the carbon image. This copypaper image can be scanned using standard imaging software, and software(e.g., ImageJ software available for download athttp://rsbweb.nih.gov/ij/) can be used to determine the number of “dots”on the image. These “dots” may be measured in pixels, and each pixel canbe correlated to a certain size to determine the size and number ofparticles. For instance, 1 pixel may correspond to 0.2646 mm, so a “dot”having a size of 1 pixel on the image may correspond to 1 particlehaving a largest dimension of 0.2646 mm; a “dot” having a size of 4pixels on the image may correspond to 1 particle having a largestdimension of 1.1 mm. Pixel sizes may vary depending on the imaginghardware and/or software used. To calculate a surface density ofparticles, wherein each of the particles has a largest cross-sectionaldimension of, for example, about 1.0 mm or greater, only the “dots”having a size of at least 4 pixels (e.g., a largest cross-sectionaldimension of about 1.0 mm or greater) would be counted. This numberwould be divided by the area of the nonwoven web and/or layer used forcounting the particles to determine the surface density of particles. Inthis particular instance, even though the nonwoven web and/or layer mayinclude some particles having a largest cross-sectional dimensionsmaller than about 1.0 mm, these particles are not accounted for thepurpose of this particular calculation.

Methods of forming nonwoven webs and/or layers having a relatively lownumber of or essentially no defects (e.g., particles on one or moresurfaces of the web) are described in more detail in U.S. PublicationNo. 2012-0152824, filed Dec. 17, 2010, and entitled, “Fine Fiber FilterMedia and Processes”.

In some embodiments, one or more nonwoven webs (e.g., in the fibrouslayer) and/or one or more layers may be formed by an electrospinningprocess. In some embodiments, electrospinning utilizes a high voltagedifferential to generate a fine jet of polymer solution from bulkpolymer solution. The jet forms as the polymer is charged by thepotential and electrostatic repulsion forces overcome the surfacetension of the solution. The jet gets drawn into a fine fiber under theeffect of repulsive electrical forces applied to the solution. The jetdries in flight and is collected on a grounded collector. The rapidsolvent evaporation during this process leads to the formation ofpolymeric nanofiber which are randomly arranged into a web. In someembodiments, electrospun fibers are made using non-melt fiberizationprocesses. Electrospun fibers can be made with any suitable polymersincluding but not limiting to, organic polymers, inorganic material(e.g., silica), hybrid polymers, and any combination thereof. In someembodiments, the synthetic fibers, described herein, may be formed froman electrospinning process.

In some embodiments, a non-wet laid process, such as an air laid orcarding process, may be used to form one or more nonwoven webs and/orone or more layers (e.g., coarse fiber layer). For example, in an airlaid process, synthetic fibers may be mixed, while air is blown onto aconveyor. In a carding process, in some embodiments, the fibers aremanipulated by rollers and extensions (e.g., hooks, needles) associatedwith the rollers. In some embodiments, one or more coarse fiber layersmay be formed from a carding process. In some cases, forming thenonwoven webs through a non-wet laid process may be more suitable forthe production of a highly porous media. In some embodiments, a blowingor spinning process may be used to form the nonwoven webs in the fibrouslayer and another non-wetlaid process (e.g., carding) may be used toform one or more coarse fiber layers (e.g., two coarse fiber layers).

In some embodiments, one or more nonwoven webs and/or one or more layers(e.g., coarse fiber layer) may be produced using a wet laid process. Ingeneral, a wet laid process involves mixing together of fibers of one ormore type; for example, polymeric staple fibers of one type may be mixedtogether with polymeric staple fibers of another type, and/or withfibers of a different type (e.g., synthetic fibers and/or naturalfibers), to provide a fiber slurry. The slurry may be, for example,aqueous-based slurry. In certain embodiments, fibers, are optionallystored separately, or in combination, in various holding tanks prior tobeing mixed together (e.g., to achieve a greater degree of uniformity inthe mixture).

During or after formation of a nonwoven web and/or coarse fiber layer,the nonwoven web and/or coarse fiber layer may be further processedaccording to a variety of known techniques. In some embodiments, one ormore nonwoven webs may be further processed to form the fibrous layer.For example, two or more nonwoven webs may be formed separately andcombined by any suitable method (e.g., calendering) to form the fibrouslayer. The two or more nonwoven webs may be formed using differentprocesses (e.g., electrospinning, meltblowing), or the same process(e.g., meltbowing). For instance, each of the nonwoven webs may beindependently formed by a non-wet laid process (e.g., meltblown process,melt spinning process, centrifugal spinning process, electrospinningprocess, dry laid process, air laid process), a wet laid process, or anyother suitable process.

In general, further processing of one or more nonwoven webs to form thefibrous layer may alter one or more properties of the nonwoven web(s).In some such embodiments, the fibrous layer may have differentproperties than the nonwoven web(s) used to form the layer. Forinstance, the fibrous layer may be more structurally uniform, have asmaller pore size (e.g., mean flow pore size, maximum pore size), have asmaller air permeability, and/or a larger basis weight than the nonwovenweb(s) used to form the fibrous layer. For example, one or more nonwovenwebs used to form the fibrous layer may have a mean flow pore size ofgreater than or equal to about 1 micron and less than or equal to about30 microns (e.g., greater than or equal to about 8 microns and less thanor equal to about 15 microns) whereas the fibrous layer may have a meanflow pore size of greater than or equal to about 1 micron and less thanor equal to about 6 microns (e.g., greater than or equal to about 2microns and less than or equal to about 5 microns). One or more nonwovenwebs used to form the fibrous layer may have a maximum pore size ofgreater than or equal to about 10 microns and less than or equal toabout 35 microns (e.g., greater than or equal to about 15 microns andless than or equal to about 25 microns) whereas the fibrous layer mayhave a maximum pore size of greater than or equal to about 4 microns andless than or equal to about 12 microns (e.g., greater than or equal toabout 6 microns and less than or equal to about 9 microns). As anotherexample, one or more nonwoven webs used to form the fibrous layer mayhave an air permeability of greater than or equal to about 10 CFM andless than or equal to about 150 CFM (e.g., greater than or equal toabout 40 CFM and less than or equal to about 100 CFM) whereas thefibrous layer may have an air permeability of greater than or equal toabout 1 CFM and less than or equal to about 10 CFM (e.g., greater thanor equal to about 4 CFM and less than or equal to about 10 CFM). One ormore nonwoven webs used to form the fibrous layer may have a basisweight of greater than or equal to about 5 g/m² and less than or equalto about 25 g/m² (e.g., greater than or equal to about 10 g/m² and lessthan or equal to about 20 g/m²) whereas the fibrous layer may have abasis weight of greater than or equal to about 10 g/m² and less than orequal to about 50 g/m² (e.g., greater than or equal to about 20 g/m² andless than or equal to about 40 g/m²). In one example, one or morenonwoven webs used to form the fibrous layer may have a thickness ofgreater than or equal to about 1 mil and less than or equal to about 7mils (e.g., greater than or equal to about 4 mils and less than or equalto about 6 mils) whereas the fibrous layer may have a thickness ofgreater than or equal to about 1 mil and less than or equal to about 6mils (e.g., greater than or equal to about 2 mils and less than or equalto about 4 mils). In general, the further processing step used to formthe fibrous layer may impart beneficial properties to the fibrous layer,such as a relatively high protection rating (e.g., ANSI/AAMI level 4).

In some embodiments, one or more nonwoven webs may undergo a calenderingstep to form the fibrous layer having different properties than thenonwoven web(s) used to form the layer. In certain embodiments,substantially all the nonwoven webs in the fibrous layer may undergo acalendering process. In some such embodiments in which the fibrous layeris formed from two or more nonwoven webs, the nonwoven webs may becalendered together. In general, calendering may involve, for example,compressing a single nonwoven web or two or more nonwoven webs (e.g.,first and second nonwoven webs) together using calender rolls under aparticular pressure, temperature, and line speed.

In general, the pressure, temperature, and line speed of the calenderingprocess may be selected to make the fibers plastic and/or change theshape of the fibers (e.g., from cylindrical to ribbon-like) withoutsignificantly changing the absolute value of the diameter of the fibers.For example, the calendaring process may change the absolute value ofthe average diameter of the fibers by less than or equal to about 0.3microns (e.g., less than or equal to about 0.2 microns). For instance,the temperature during calendering may be less than the meltingtemperature of one or more of the polymers (e.g., one polymer, allpolymers) in the nonwoven web(s). For example, when the nonwoven web(s)comprise polypropylene fibers, the calendering temperature may be lessthan the melting temperature of the polypropylene fibers. In certainembodiments, the temperature may be less than or equal to about 100° C.,less than or equal to about 95° C., less than or equal to about 90° C.,or less than or equal to about 85° C. and/or greater than or equal toabout 75° C. In some embodiments, a relatively high calendering pressuremay be used. For instance, the pressure may be greater than or equal toabout 450 pounds per linear inch (e.g., greater than or equal to about700 pli). In some embodiments, the pressure may be between about 450 plito about 900 pli (e.g., between about 700 pli to about 900 pli). Theline speed may be between about 5 ft/min to about 100 ft/min (e.g.,between about 5 ft/min to about 80 ft/min, between about 10 ft/min toabout 50 ft/min, between about 15 ft/min to about 100 ft/min, or betweenabout 20 ft/min to about 90 ft/min).

In other embodiments, one or more layers may be uncalendered. Forexample, one or more coarse layers may not undergo a calendering processand may be combined to the fibrous layer using another process (e.g., byadhesives).

Non-limiting examples of other further processing steps includelamination, co-pleating, and collation. In some embodiments, a furtherprocessing step may be used to add additional nonwoven webs to a layerand/or the protective clothing material. As described herein, in someembodiments two or more nonwoven webs and/or two or more layers of theprotective clothing material may be formed separately and combined byany suitable method (such as lamination, calendering, collation), or byuse of adhesives which may be preferred in certain cases. In some suchembodiments, two or more layers may be formed using different processes(e.g., meltblowing, carding), or the same process (e.g., meltbowing).For example, each of the layers may be independently formed by a non-wetlaid process (e.g., meltblown process, melt spinning process (e.g.,spunbond process), centrifugal spinning process, electrospinningprocess, dry laid process, air laid process).

As noted above, in some embodiments, the fibrous layer and coarse fiberlayer(s) may be combined using an adhesive. For instance, the layers(e.g., fibrous layer and coarse fiber layer(s)) may be adhered usingadhesives, such that the layers (e.g., fibrous layer and coarse fiberlayer(s)) are adhesively bound. In some of these embodiments, thefibrous layer is calendered and subsequently combined with the coarsefiber layer(s) (e.g., two coarse fiber layers) using an adhesive. Insuch embodiments, the coarse fiber layer(s) may be uncalendered. Such aconstruction may exhibit particularly attractive properties, forexample, as compared to constructions that include similar layers thatare combined entirely using a calendering process. Non-limiting examplesof suitable adhesives include ethyl vinyl acetate (EVA), copolyesters,polyolefins, polyamides, polyurethanes, styrene block copolymers,thermoplastic elastomers, polycarbonates, silicones, and combinationsthereof. Adhesives can be applied using different methods like spraycoating (solution spraying if solvent or water based adhesives are usedor melt spraying if hot melt adhesive is used), dip coating, kiss roll,knife coating, and gravure coating.

Lamination may involve, for example, compressing two or more webstogether using a flatbed laminator or any other suitable device at aparticular pressure and temperature for a certain residence time (i.e.,the amount of time spent under pressure and heat). For instance, thepressure may be between about 5 psi to about 150 psi (e.g., betweenabout 30 psi to about 90 psi, between about 60 psi to about 120 psi,between about 30 and 60 psi, or between about 90 psi and about 120 psi);the temperature may be between about 75° F. and about 400° F. (e.g.,between about 75° F. and about 300° F., between about 200° F. and about350° F., or between about 275° F. and about 390° F.); and the residencetime between about 1 second to about 60 seconds (e.g., between about 1second to about 30 seconds, between about 10 second to about 25 seconds,or between about 20 seconds and about 40 seconds). Other ranges forpressure, temperature, and residence time are also possible.

In some embodiments, the one or more nonwoven webs may include one ormore additives (e.g., a lubricant, a slip agent, a surfactant, acoupling agent, a crosslinking agent). In certain instances, one or moreadditives can be used to reduce or eliminate the number of polymericparticles formed on or in the nonwoven web(s).

As noted above, in some embodiments, one or more nonwoven webs, one ormore layers (e.g., coarse fiber layer, fibrous layer), and/or theprotective clothing material may be modified with a material. Ingeneral, any suitable method for modifying the surface and/or theinterior of a nonwoven web, layer, or protective clothing material maybe used, such as melt additives and coating. In some embodiments, thesurface and/or interior of a nonwoven web, layer, or protective clothingmaterial may be modified by coating at least a portion of the surfaceand/or interior. In certain embodiments, a coating process involvesintroducing resin or a material (e.g., hydrophobic material) dispersedin a solvent or solvent mixture onto a pre-formed nonwoven web, layer,or protective clothing material (e.g., a pre-formed nonwoven web formedby a wetlaid process, meltblown process, etc.). Non-limiting examples ofcoating methods include the use of vapor deposition (e.g., chemicalvapor, physical vapor deposition), layer-by-layer deposition,wax-solidification, self-assembly, sol-gel processing, a slot diecoater, gravure coating, screen coating, size press coating (e.g., a tworoll-type or a metering blade type size press coater), film presscoating, blade coating, roll-blade coating, air knife coating, rollcoating, foam application, reverse roll coating, bar coating, curtaincoating, champlex coating, brush coating, Bill-blade coating, shortdwell-blade coating, lip coating, gate roll coating, gate roll sizepress coating, laboratory size press coating, melt coating, dip coating,knife roll coating, spin coating, spray coating (e.g., electrospraying),gapped roll coating, roll transfer coating, padding saturant coating,and saturation impregnation. Other coating methods are also possible. Insome embodiments, the material (e.g., hydrophobic material) may beapplied to the nonwoven web using a non-compressive coating technique.The non-compressive coating technique may coat the nonwoven web, whilenot substantially decreasing the thickness of the web. In otherembodiments, the resin may be applied to the nonwoven web using acompressive coating technique.

In one set of embodiments, a surface and/or interior of a nonwoven web,layer, or protective clothing material is modified using chemical vapordeposition, e.g., at least a portion of a surface of, interior of,and/or an entire nonwoven web, layer, or protective clothing materialmay comprise a chemical vapor deposition coating. In chemical vapordeposition, the nonwoven web is exposed to gaseous reactants from gas orliquid vapor that are deposited onto the nonwoven web under high energylevel excitation such as thermal, microwave, UV, electron beam orplasma. Optionally, a carrier gas such as oxygen, helium, argon and/ornitrogen may be used.

Other vapor deposition methods include atmospheric pressure chemicalvapor deposition (APCVD), low pressure chemical vapor deposition(LPCVD), metal-organic chemical vapor deposition (MOCVD), plasmaassisted chemical vapor deposition (PACVD) or plasma enhanced chemicalvapor deposition (PECVD), laser chemical vapor deposition (LCVD),photochemical vapor deposition (PCVD), chemical vapor infiltration (CVI)and chemical beam epitaxy (CBE).

In physical vapor deposition (PVD) thin films are deposited by thecondensation of a vaporized form of the desired film material ontosubstrate. This method involves physical processes such ashigh-temperature vacuum evaporation with subsequent condensation, orplasma sputter bombardment rather than a chemical reaction.

After applying the coating to the nonwoven web, layer, or protectiveclothing material, the coating may be dried by any suitable method.Non-limiting examples of drying methods include the use of a photodryer, infrared dryer, hot air oven steam-heated cylinder, or anysuitable type of dryer familiar to those of ordinary skill in the art.

In some embodiments, at least a portion of the fibers of a nonwoven web,layer, or protective clothing material may be modified (e.g., coated)without substantially blocking the pores of the nonwoven web. In someinstances, substantially all of the fibers may be coated withoutsubstantially blocking the pores. In some embodiments, the nonwoven web,layer, or protective clothing material may be coated with a relativelyhigh weight percentage of resin or material without blocking the poresof a nonwoven web, layer, or protective clothing material using themethods described herein (e.g., by dissolving and/or suspending one ormore material in a solvent to form the resin).

In some cases, a melt additive may be incorporated into at least aportion of the fibers in a nonwoven web, layer, and/or protectiveclothing material to modify the nonwoven web, layer, and/or protectiveclothing material. For example, in certain embodiments, a melt additivemay be used to modify the hydrophobicity of at least a surface of thenonwoven web, layer, and/or protective clothing material.

In some cases, the melt additive may comprise a preblended masterbatchmelt additive. Preblended masterbatch melt additives are known in theart and one of ordinary skill would be capable of incorporatingpreblended masterbatch melt additives into fibers based upon theteachings of this specification. A preblended masterbatch melt additivemay be used to make hydrophobic fibers, which may be used to make atleast a portion of the nonwoven webs, layers, and/or protective clothingmaterials hydrophobic.

In general, any suitable material may be used to alter the chemistry(e.g., surface chemistry), and accordingly the wettability, of anonwoven web, layer, or protective clothing material.

In general, the net charge of the modified portion of nonwoven web,layer, or protective clothing material (e.g., surface, interior) may benegative, positive, or neutral. In some embodiments, the nonwoven web,layer, or protective clothing material (e.g., surface) may be modifiedwith an electrostatically neutral material. In some embodiments, smallmolecules may be used to modify at least one surface and/or interior ofa nonwoven web, layer, or protective clothing material. In certainembodiments, the small molecule may be an inorganic or organichydrophobic molecule. Non-limiting examples include hydrocarbons (e.g.,CH₄, C₂H₂, C₂H₄, C₆H₆), fluorocarbons (e.g., CF₄, C₂F₄, C₃F₆, C₃F₈,C₄H₈, C₅H₁₂, C₆F₆), silanes (e.g., SiH₄, Si₂H₆, Si₃H₈, Si₄H₁₀),organosilanes (e.g., methylsilane, dimethylsilane, triethylsilane),siloxanes (e.g., dimethylsiloxane, hexamethyldisiloxane), ZnS, CuSe,InS, CdS, tungsten, silicon carbide, silicon nitride, siliconoxynitride, titanium nitride, carbon, silicon-germanium, and hydrophobicacrylic monomers terminating with alkyl groups and their halogenatedderivatives (e.g., ethyl 2-ethylacrylate, methyl methacrylate;acrylonitrile). In certain embodiments, suitable hydrocarbons formodifying a surface of a layer may have the formula C_(x)H_(y), where xis an integer from 1 to10 and y is an integer from 2 to 22. In certainembodiments, suitable silanes for modifying a surface of a layer mayhave the formula Si_(n)H_(2n+2) where any hydrogen may be substitutedfor a halogen (e.g., Cl, F, Br, I), and where n is an integer from 1 to10.

As used herein, “small molecules” refers to molecules, whethernaturally-occurring or artificially created (e.g., via chemicalsynthesis) that have a relatively low molecular weight. Typically, asmall molecule is an organic compound (i.e., it contains carbon). Thesmall organic molecule may contain multiple carbon-carbon bonds,stereocenters, and other functional groups (e.g., amines, hydroxyl,carbonyls, and heterocyclic rings, etc.). In certain embodiments, themolecular weight of a small molecule is at most about 1,000 g/mol, atmost about 900 g/mol, at most about 800 g/mol, at most about 700 g/mol,at most about 600 g/mol, at most about 500 g/mol, at most about 400g/mol, at most about 300 g/mol, at most about 200 g/mol, or at mostabout 100 g/mol. In certain embodiments, the molecular weight of a smallmolecule is at least about 100 g/mol, at least about 200 g/mol, at leastabout 300 g/mol, at least about 400 g/mol, at least about 500 g/mol, atleast about 600 g/mol, at least about 700 g/mol, at least about 800g/mol, or at least about 900 g/mol, or at least about 1,000 g/mol.Combinations of the above ranges (e.g., at least about 200 g/mol and atmost about 500 g/mol) are also possible.

In some embodiments, polymers may be used to modify at least one surfaceand/or interior of a nonwoven web, layer, or protective clothingmaterial. For example, one or more polymers may be applied to at least aportion of a surface and/or interior of a nonwoven web, layer, orprotective clothing material via a coating technique. In certainembodiments, the polymer may be formed from monobasic carboxylic acidsand/or unsaturated dicarboxylic (dibasic) acids. In certain embodiments,the polymer may be a graft copolymer and may be formed by graftingpolymers or oligomers to polymers in the fibers and/or nonwoven web(e.g., resin polymer). The graft polymer or oligomer may comprisecarboxyl moieties that can be used to form a chemical bond between thegraft and polymers in the fibers and/or nonwoven web. Non-limitingexamples of polymers in the fibers and/or nonwoven web that can be usedto form a graft copolymer include polyethylene, polypropylene,polycarbonate, polyvinyl chloride, polytetrafluoroethylene, polystyrene,cellulose, polyethylene terephthalate, polybutylene terephthalate, andnylon, and combinations thereof. Graft polymerization can be initiatedthrough chemical and/or radiochemical (e.g., electron beam, plasma,corona discharge, UV-irradiation) methods.

In some embodiments, a gas may be used to modify at least one surfaceand/or interior of a nonwoven web, layer, or protective clothingmaterial. In some such cases, the molecules in the gas may react withmaterial (e.g., fibers, resin, additives) on the surface of a nonwovenweb, layer, or protective clothing material to form functional groups,such as charged moieties, and/or to increase the oxygen content on thesurface of the layer. Non-limiting examples of functional groups includehydroxyl, carbonyl, ether, ketone, aldehyde, acid, amide, acetate,phosphate, sulfite, sulfate, amine, nitrile, and nitro groups.Non-limiting examples of gases that may be reacted with at least onesurface of a layer (e.g., modified) includes CO₂, SO₂, SO₃, NH₃, N₂H₄,N₂, H₂, He, Ar, and air, and combinations thereof.

The protective clothing material may include any suitable number ofnonwoven webs, e.g., at least 2, at least 3, at least 4, at least 5, atleast 6, at least 7, at least 8, or at least 10 nonwoven webs. In someembodiments, the protective clothing material may include up to 20nonwoven webs.

In some embodiments, a layer described herein may be or include anonwoven web. A nonwoven web may include non-oriented fibers (e.g., arandom arrangement of fibers within the web). Examples of nonwoven websinclude webs made by wet-laid or non-wet laid processes as describedherein.

The protective clothing material may be incorporated into a variety ofprotective garments for use in various environments including operatingrooms or anywhere else ANSI/AAMI level 4 protective garments are needed.The protective clothing material may be used to form surgical apparel(e.g., surgical hoods, surgical gown). The term “surgical apparel” hasits ordinary meaning in the art and may be in accordance with the 21C.F.R. § 878.4040(a) (2012). For example, surgical apparel may be adevice that is intended to be worn by operating room personnel duringsurgical procedures to protect both the surgical patient and theoperating room personnel from transfer of microorganisms, body fluids,and particulate material. Non-limiting examples include surgical caps,hoods, masks, gowns, operating room shoes and shoe covers, and isolationmasks and gowns. In certain embodiments, the protective clothingmaterial may be used to form surgical drapes. The term “surgical drape”has its ordinary meaning in the art and may be in accordance with the 21C.F.R. § 878.4370(a) (2012). For example, a surgical drape may be adevice made of natural or synthetic materials intended to be used as aprotective patient covering, such as to isolate a site of surgicalincision from microbial and other contamination. In certain embodiments,the device may include a plastic wound protector that may adhere to theskin around a surgical incision or be placed in a wound to cover itsexposed edges. In some instances, the device may include aself-retaining finger cot that is intended to allow repeated insertionof the surgeon's finger into the rectum during performance of atransurethral prostatectomy. One of ordinary skill in the art would beknowledgeable about methods of forming surgical garments from protectiveclothing material. In general, the protective clothing material is cutand sewn together as in traditional garment manufacturing, except heatsealing and/or ultrasonic seaming are used instead of traditional sewingtechniques involving thread. Heat sealing or ultrasonic seaming is usedto form a good seal (e.g., impermeable seal), while maintaining theintegrity of the garment and barrier protection.

During use, the protective clothing materials mechanically trapcontaminants (e.g., bodily fluid, microbes) and prevents strikethrough.The protective clothing materials need not be electrically charged toenhance trapping of contamination. Thus, in some embodiments, theprotective clothing materials are not electrically charged. However, insome embodiments, the protective clothing materials may be electricallycharged.

EXAMPLES Example 1

This example describes a protective clothing material including acalendered layer positioned between two coarse fiber nonwoven webs. Theprotective clothing material had a ANSI/AAMI level 4 protection rating,a high air permeability, low basis weight, and uniform structuralproperties. A protective clothing material containing a first coarsefiber nonwoven web, a calendered layer including two nonwoven webs, anda second coarse fiber nonwoven web was formed. The calendered layer wasdirectly adjacent to the first and second coarse fiber nonwoven webs.

The calendered layer included a first nonwoven web and a second nonwovenweb that were calendered together after formation. Before calendering,the first and second nonwoven webs each included meltblown polypropylenefibers having an average fiber diameter of 0.8 microns, had a basisweight of about 15 g/m², had a mean flow pore size of 9.1 microns, had amaximum pore size of about 20.7 microns, and an air permeability ofabout 48 CFM. The calendered layer had a basis weight of about 30 g/m²,a mean flow pore size of 2.9 microns, a maximum pore size of about 7.3microns, and an air permeability of about 4.4 CFM. The first and secondcoarse nonwoven webs were formed by a spunbond process and includedpolypropylene staple fibers having an average fiber diameter of 20microns. The protective clothing material was formed by adhesivelybonding the coarse fiber nonwoven webs to the calendered layer. Scanningelectron microscope images of the calendered layer before (top) andafter (bottom) calendering at an 1000× magnification and a 2500×magnification are shown in FIGS. 6A and 6B, respectively.

The properties of the protective clothing material, the comparativematerial of Comparative Example 1, and the existing material ofComparative Example 2 are shown in Table 1. Unless otherwise indicated,the structural and performance properties of the layers and entireprotective clothing material were measured as described herein.

TABLE 1 Properties of the Protective Clothing Material, ComparativeMaterial, and Conventional Material Protective Clothing ComparativeExisting Property Material Material Material ASTM Pass Fail Pass 1670 -08(2014)e1 ASTM Pass Fail Pass 1671 - 13 (2013) Basis weight 62 g/m² 62g/m² 72 g/m² Air 4.4 CFM 22 CFM 0.11 CFM permeability Std. dev. 0.71 CFM2.2 CFM — in air permeability Thickness 12 mils 18 mils 12 mils Meanflow 3 microns 6.7 microns 0.4 microns pore size Maximum 7 microns 17.2microns 1.1 microns pore size

As shown in Table 1, the protective clothing material including acalendered layer passed ASTM 1670-08(2014)e1 and ASTM 1671-13 (2013)while having a relatively high air permeability and a relatively lowbasis weight and thickness.

Comparative Example 1

This example describes a comparative material including an uncalenderedlayer positioned between two coarse fiber nonwoven webs. The comparativematerial was formed as described in Example 1, except the first nonwovenweb and the second nonwoven web were not calendered together afterformation. The comparative material had a higher pore size, airpermeability, and standard deviation in air permeability, but failedASTM 1670-08(2014) el and ASTM 1671-13.

Comparative Example 2

This example describes an existing protective clothing materialincluding film positioned between inner and outer fabric layers made ofcontinuous fine filaments. The existing protective clothing material hada similar thickness, and protective rating as the protective clothingmaterial in Example 1, but had a significantly lower air permeabilityand pore size.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. A protective clothing material, comprising: afibrous layer comprising synthetic fibers, wherein: a mean flow poresize of the fibrous layer is greater than or equal to about 1 micron andless than or equal to about 6 microns, a maximum pore size of thefibrous layer is greater than or equal to about 4 micron and less thanor equal to about 12 microns, a difference between the maximum pore sizeand the mean pore size is less than or equal to about 6 microns, and anair permeability of the fibrous layer is greater than or equal to about4 CFM and less than or equal to about 10 CFM.
 2. The protective clothingmaterial of claim 1, wherein the protective clothing material isconfigured as a surgical apparel or a surgical drape.
 3. The protectiveclothing material of claim 1, wherein the average diameter of thesynthetic fibers is greater than or equal to about 0.01 microns and lessthan or equal to about 10 microns.
 4. The protective clothing materialof claim 1, wherein the fibrous layer is a calendered layer.
 5. Theprotective clothing material of claim 1, wherein the mean flow pore sizeof the fibrous layer is greater than or equal to about 2 microns andless than or equal to about 5 microns.
 6. The protective clothingmaterial of claim 5, wherein the maximum pore size of the fibrous layeris greater than or equal to about 6 microns and less than or equal toabout 9 microns.
 7. (canceled)
 8. A protective clothing material,comprising: a fibrous layer comprising synthetic fiber, wherein a meanflow pore size of the fibrous layer is greater than or equal to about 1micron and less than or equal to about 6 microns, a standard deviationof the mean flow pore size of the fibrous layer is greater than or equalto about 0 microns and less than or equal to about 1 micron, and astandard deviation of an air permeability of the fibrous layer isgreater than or equal to about 0 CFM and less than or equal to about 1CFM.
 9. The protective clothing material of claim 8, wherein theprotective clothing material is configured as a surgical apparel or asurgical drape.
 10. (canceled)
 11. The protective clothing material ofclaim 8, wherein a basis weight of the fibrous layer is greater than orequal to about 10 g/m² and less than or equal to about 50 g/m².
 12. Theprotective clothing material of claim 8, wherein the synthetic fibersare polypropylene fibers.
 13. (canceled)
 14. A protective clothingmaterial, comprising: a first coarse fiber layer; a second coarse fiberlayer; and a fibrous layer positioned between the first and the secondcoarse fiber layers, wherein the fibrous layer comprises a meltblownfiber web, has a mean flow pore size of greater than or equal to about 1micron and less than or equal to about 6 microns, has an airpermeability of greater than or equal to about 1 CFM and less than orequal to about 10 CFM, and has a basis weight of greater than or equalto about 10 g/m² and less than or equal to about 50 g/m².
 15. Theprotective clothing material of claim 14, wherein the protectiveclothing material is configured as a surgical apparel or a surgicaldrape.
 16. The protective clothing material of claim 14, wherein themaximum pore size of the fibrous layer is greater than or equal to about4 microns and less than or equal to about 12 microns
 17. The protectiveclothing material of claim 14, wherein a standard deviation in mean flowpore size of the fibrous layer is greater than or equal to about 0microns and less than or equal to about 2 microns.
 18. The protectiveclothing material of claim 14, wherein the fibrous layer has a thicknessof greater than or equal to about 1 mil and less than or equal to about6 mils.
 19. The protective clothing material of claim 14, wherein amoisture vapor transmission rate of the fibrous layer is greater than orequal to about 1,000 g/m².day and less than or equal to about 5,000g/m².day.
 20. The protective clothing material of claim 14, wherein thebasis weight of the fibrous layer is greater than or equal to about 20g/m² and less than or equal to about 40 g/m².
 21. The protectiveclothing material of claim 14, wherein the first coarse fiber layer isadhesively bonded to the fibrous layer.
 22. (canceled)
 23. Theprotective clothing material of claim 14, wherein the first coarse fiberlayer, the second coarse fiber layer, and the fibrous layer are notcalendered together. 24-25. (canceled)
 26. The protective clothingmaterial of claim 14, wherein the meltblown fiber web, the first coarsefiber layer, and the second coarse fiber layer comprise the samepolymer. 27-31. (canceled)
 32. The protective clothing material of claim14, wherein the protective clothing material has an air permeability ofgreater than or equal to about 1 CFM and less than or equal to about 10CFM. 33-36. (canceled)
 37. A method of forming a protective clothingmaterial, comprising: providing a plurality of nonwoven webs;calendering the plurality of nonwoven webs to form a fibrous layer,wherein the fibrous layer has an air permeability of greater than orequal to about 4 CFM and less than or equal to about 10 CFM, an airpermeability uniformity of the layer is greater than or equal to about 0and less than or equal to about 1, and a mean flow pore size of greaterthan or equal to about 1 micron and less than or equal to about 6microns; and adhering a coarse fiber layer to at least one surface ofthe fibrous layer using an adhesive. 38-40. (canceled)